Fitness is a property of an allele that refers to its relative likelihood of representation in future generations in a population. An allele with higher fitness will be more likely to be represented in future generations within a population than an allele for the same gene with lower fitness. The important thing here is that the likelihood of future representation has to be due to a feature of that allele, and not random effects.

At first glance RS and Fitness are the same, or similar, but one might immediately notice that RS is a feature of an individual (that has offspring) while fitness is a feature of an allele. So, it is possible that a given individual will have a relatively high RS but contain a particular allele with low fitness. Presumably the higher RS of that individual is due to high-fitness alleles of other genes. In this way, fitness and RS are different, but when considering large scales of time and large populations, the two can be (perhaps) safely conflated because things average out over time and the different alleles are being independently assorted over generational time, so each allele gets to have its day, sometimes, independently of other lower-fitness alleles. By this way of thinking, RS and fitness can be safely considered as measures of roughly the same thing, but with caveats.

RS is usually measured, in actual experimental work or field observations, as the number of offspring observed for an individual, but to make sure that RS is correlated with fitness, one might measure grand-offspring in order to factor out infertile offspring and other factors that may affect one generation but that do not apply over the long term. Again, RS and fitness are then, it would seem, equatable but with caveats.

RS is the number of offspring or grand-offspring but kin selection may apply as well. This is where an individual foregoes some of its own reproduction for the benefit of a relative, causing indirect fitness, a measure of this contribution devalued by the probability of the two individuals sharing the same allele by common descent. One can state that a measure of RS is still a measure of fitness because over the long term, again, things average out, but equating fitness and RS is done, again, with caveats.

There may be an optimal number of offspring an individual may have, above which longer term reproduction is reduced. A litter that is too large may result in a set of adults that are smaller than ideal and will thus have fewer offspring, or in the case of serial reproduction, if parental investment is spread out over several offspring, having too many offspring in a row may cause a deficit for all of the offspring, or for the later offspring that get less care because less energy is available, or earlier offspring may get short changed by being left on their own sooner. Putting this another way, the ultimate long-germ fitness strategy may be to have X offspring, where having more or fewer than X results in a suboptimal outcome. In this way, increasing RS from zero towards X increases fitness, but increasing RS beyond X decreases fitness.

So, RS equals fitness except:

• RS is a measure applied to an individual while fitness is ideally applied to alleles for a gene or some other genetic construct;
• The offspring-fertility link can be misleading. A queen bee with an allele that allows her to produces more sterile offspring may also produce more fertile offspring;
• RS is fitness plus or minus random effects;
• RS usually does not consider indirect fitness;
• RS is selected to be optimized while fitness is selected to be maximized.

Equating RS and fitness is therefore only a rough approximation. When initially learning about Natural Selection students are often led to believe that RS and fitness are the same, which is only true with these (and possibly other) caveats. Equating RS and fitness in pedagogy risks skipping past and perhaps never understanding the caveats, and these caveats are very far from trivial. They are, in many cases, the point of specific evolutionary research projects.

But of course, he did, and the new research being referred to does not “disprove darwin.”

At least the piece I’m referring to here takes a somewhat tongue in cheek attitude towards the story.

“Survival of the fittest,” the Darwinian theory that has been absorbed as scientific fact for the last 150 years, has finally been disproven. A new study published in the highly respected journal “Biology Letters” has proved that creationism and immaculate conception as not only scientifically valid, but true beyond any reasonable doubt.

Just kidding…

Yes, it seems to be a joke, but this particular writeup by Carmel Lobello still mindlessly reports that the new research “contradicts Darwin’s most important work.”

No it doesn’t.

I think the root of this problem may be in the press office linked to the paper itself, or may be the authors. Nimrods.

In an article titled “Space is the final frontier for evolution, study claims” BBC “science writer” Howard Falcon-Lang uses the old, tired, and quite frankly, stupendously unethical tack of making a claim that Darwin has been overthrown by new research. If someone actually overthrows Darwin, then so be it. But this is not what has happened. Falcon-Lang, or perhaps his BBC handlers, have used the cheap trick to sell their wares, and this is not appreciated.

If Howard Falcon-Lang did not a) claim to be a science reporter and b) have a dumb-ass hyphenated name, I’d be nice in my critique of his recent writeup. But no. He left me no choice. I will have to take it apart red in tooth and claw.

Charles Darwin may have been wrong when he argued that competition was the major driving force of evolution.

OK, this is a little premature for me to say here, but as you read on you’ll see that my assertion is justified: Mr. Falcon-Lang is not really in a position to make any kind of claim regarding the wrongness or rightness of a genius of the level of Dr. Darwin.

He imagined a world in which organisms battled for supremacy and only the fittest survived.

No. That is the world that so many hack science writers, creationists, and various Darwin detractors imagine. Darwin wrote endlessly about differential survival, differential reproduction, mate selection, and all the myriad forces that determine selection (and randomness). He did not imagine the thing Mr. Falcon-Lang imagines him to have imagined.

But new research identifies the availability of “living space”, rather than competition, as being of key importance for evolution.

Never start a sentence, let alone a paragraph, with the word “but” especially when the rest of the essay is something one has essentially pulled out of one’s “butt.”

Now, a reality check: Living space, including nesting sites, feeding territories, reproductive or social territories, and just having space for a number of reasons has been on the books as a thing to compete over since … well, since Darwin first talked about it. So has the actual focus of the paper in question: Niche space. Sub-habitats or resources that can be exploited by a particular type of organism. You know the drill: The woodpecker niche, the soil detritus niche, the niche of flight, etc. to which organisms are constantly shifting their adaptive positions. More of those equals more types of organisms, and since most species can not be of more than one ‘type’ (though some can, interestingly) that also means more species diversity.

Findings question the old adage of “nature red in tooth and claw”.

I’m pretty sure this sentence/paragraph was supposed to be a heading but some dumb-ass editor screwed up. In any event, yes, there is an adage. We do not do science with adages. A science writer should know that. Adage indeed. There is also an old adage that one should never believe what is written by the press.

The rest of the essay is a description of the research, and is not terrible. Of course, Pagel and colleagues demonstrated that part of the key effect that is being observed here some years ago when they showed that species diversity correlates to the width of the continent better than to latitude in the New World, thus offering a better explanation for the pattern of species diversity than the “the equator has got lots of it” hypothesis. The rest of it: niche space, we also already had a good idea about, but this new study is more comprehensive and much larger scale.

Focusing on land animals – amphibians, reptiles, mammals and birds – the scientists showed that the amount of biodiversity closely matched the availability of “living space” through time.

Living space – more formally known as the “ecological niche concept” by biologists – refers to the particular requirements of an organism to thrive. It includes factors like the availability of food and a favourable habitat.

The new study proposes that really big evolutionary changes happen when animals move into empty areas of living space, not occupied by other animals.

For example, when birds evolved the ability to fly, that opened up a vast range of new possibilities not available to other animals. Suddenly the skies were quite literally the limit, triggering a new evolutionary burst.

This concept challenges the idea that intense competition for resources in overcrowded habitats is the major driving force of evolution.

OK, let’s put aside the press report at this time. I’ll just say this: It is quite possible that Mr. Falcon-Lang was the victim of some very bad messing around by an editor who is not a science writer. At the BBC. If so, I hope he lets us know that so we can all write letters of complaint to said editor.

Getting back to the point at hand, what the paper actually says is this, from the abstract:

Tetrapod biodiversity today is great; over the past 400 Myr since vertebrates moved onto land, global tetrapod diversity has risen exponentially, punctuated by losses during major extinctions. There are links between the total global diversity of tetrapods and the diversity of their ecological roles, yet no one fully understands the interplay of these two aspects of biodiversity and a numerical analysis of this relationship has not so far been undertaken. Here we show that the global taxonomic and ecological diversity of tetrapods are closely linked. Throughout geological time, patterns of global diversity of tetrapod families show 97 per cent correlation with ecological modes. Global taxonomic and ecological diversity of this group correlates closely with the dominant classes of tetrapods (amphibians in the Palaeozoic, reptiles in the Mesozoic, birds and mammals in the Cenozoic). These groups have driven ecological diversity by expansion and contraction of occupied ecospace, rather than by direct competition within existing ecospace and each group has used ecospace at a greater rate than their predecessors.

The idea of empty niches being filled by the available taxa is not new, nor is the idea that an evolutionary “event” …. like some non-flying taxon developing the power of flight …. results in species radiation. What is new in this paper is that a survey has been done using relatively good available data that demonstrates this concept.

There has not been an overthrow of Darwin, though I’m sure various creationists will now incorrectly and inappropriately use this press report to suggest that there has been. There has not been the introduction of a new idea regarding macroevolution, though the work here is important and interesting. As is often the case with evolutionary biology, the specific role of natural selection (and in this entire discussion, read “natural selection” when you see “competition”) vs. opportunity (read “drift”), and different people with different views will differentially see the role of one or the other as more important as they look at the same data. The realty of the situation is probably simpler: Competitive advantages have a chance of winning out, in the same way that buying a lottery ticket with better odds makes you more likely to win. But you’ll probably still lose. But to even buy the lottery ticket, there has to be one of those little gas stations on the corner that sells them.

Pagel, M., May, R., & Collie, A. (1991). Ecological Aspects of the Geographical Distribution and Diversity of Mammalian Species The American Naturalist, 137 (6) DOI: 10.1086/285194

Sahney, S., Benton, M., & Ferry, P. (2010). Links between global taxonomic diversity, ecological diversity and the expansion of vertebrates on land Biology Letters, 6 (4), 544-547 DOI: 10.1098/rsbl.2009.1024

Then a flood came. The stream near her chosen lair swelled its banks and threatened to drown the kittens. So, she carried one of the kittens up the hill to a new lair. She went back to get the second kitten, and the flood waters were even higher and closer to the den, but she managed to save that second kitten. When she went back to get the third kitten, it was not at all clear that she would make it in time. It seemed inevitable that the third kitten would be carried off to it’s death by the torrent. As the mother cougar approached the flood and all hope seemed to diminish, the narrator said “The mother cougar, driven by an instinct to save her species, searched desperately for any sign of the third kitten, who represented the next generation of cougars.” (Or words to that effect.)

At the last second, the mother cougar spotted the kitten, who had already run partly up the hill, and brought it safely to the lair. (We presume that all kittens always survive, which is why we are up to our necks in cougars.)

Within biology, many of the falsehoods being discussed here actually affect practicing scientists. We’ll see an especially good example of this later with the “reproductive success is maximized by fitness” fallacy. We’ve already seen it with the “Evolution has stopped for humans” fallacy. But the “Survival of the species” fallacy never directly affects actual biologists because it is literally almost the first thing you learn about selection, evolution, organismic biology, or whole organism biology. Individuals act in their own (inclusive) self interest. The appearance of altruism is usually underlain by selfish motives. If there is any group-level selection at all (and most biologists think there is not, or at least not much) it is certainly not operating at the level of the species.

The mother cougar was not trying to save cougars when she desperately searched for the third kitten. She was, rather, doing two things simultaneously.

1) She was, at some ultimate level not cognizant to her in any way, trying to increase the likelihood of the survival of her own genes. Or, more accurately, some of the genes she carried were busy saving themselves, and for this particular event, the other genes were free-riding. During some other episode of her life, perhaps as hunger drives her to hunt, different genes are perhaps busy saving themselves while the others are free-riding. I’m sure you get the picture.

…and…

2) She was, at the more immediate, or as we like to say, proximate level, her behavior was a response to some kind of limbic and endocrine attachment syndrome whereby mothers bond to and do things for their offspring, similar to the kinds of deep neurological systems that may facilitate the orientation of offspring to their mothers, and in the case of these kittens, the neuro-muscular system that causes a kitten to go limp when picked up by the nape to be carried by mom, instead of squirming around, flying out of mom’s mouth, and dropping fatally into the rushing river.

That the saving of the individual kittens would possibly help the survival of the species is a side effect of her behavior at both the proximate and ultimate level.

This idea can be tested, and has been tested, both in theoretical constructs and in field studies. It is often possible to construct alternative testable hypotheses, one based on an instinct to help the species, or some other large group, and the other to at selfishly. Below, I recommend texts you may wish to consult for excellent overviews and evidence along these lines.

The bottom line is this: A variant of a gene (an “allele”) that confers a trait that results in group-level or species-level survival or reproduction at the expense of the individual will have lower fitness than an allele that instead confers a trait that results in individual survival or reproduction. One of the classic examples of this phenomenon is the prudential restraint in egg laying among colonial nesting birds.

Some bird species — such as gulls, terns, boobies, and the like — nest communally and from these nests forage for nearby resources to feed themselves and their growing young. So, there may be dozens, hundreds, or even thousands of gull nests on well protected cliffs overlooking the ocean, and the gulls will go down to the ocean (one member of the pair at a time, the other staying behind to protect the egg or chick from the other gulls) to feed, and bringing back food for the mate and/or offspring.

The following has been noted (slightly oversimplified here):

1) The number of eggs that a pair will have in a nest varies, let’s say from 3 to 5.
2) The number of eggs each pair has in a given year is the same, with most of the birds laying 3, 4, or 5 eggs.
3) The number of eggs, higher or lower or median, appears to vary with the availability of resources. When there are lots of resources, more eggs are laid, when resources are scarce, fewer eggs are laid, to the extent that this can be assessed by the birds.

Two different hypotheses have been proposed to explain these behaviors.

A: The birds are practicing prudential restraint for the benefit of the group. By holding back on egg laying, the demand on the local resources will be lowered now and over the near future when the offspring fledge, so there will not be as much competition for resources and more members of the group will survive. This is group selection, and taken just one step more, survival of the species.

B: Individual birds (or pairs of birds, but really, probably just the female) lay the number of eggs that matches some perception about the availability of resources, and the birds are essentially tracking the resources and producing the number of offspring that makes sense, economically/ecologically, that year.

One way to test this is to place extra eggs in a small number of nests. If only a few extra eggs are placed overall (but say one per nest), that will not measurably affect the overall availability of or competition for resources by the group, but it may severely affect the birds with the loaded-up nest. Extra egg experiments have been done, and when extra eggs are added to the nest, the final number of offspring fledged goes down rather than up. In other words, the number of eggs in an individual nest is adjusted as needed for the individual’s fitness, not the group’s fitness.

Another fact worth noting is that if both parents in these colonial nesters leave the nest alone, the neighboring birds tend to eat the eggs or chicks as a snack. So much for survival of the species. One would think that if you could prudentially restraining one’s reproduction as an evolutionary strategy, one would prudentially restrain one’s snacking behavior for the same purpose.

It is interesting to note that the survival of the species fallacy has other forms in other areas that are very important. The survival of the species problem is the same problem as the tragedy of the commons problem. It is also the same thing as the “agency effect” or the “agency problem.” It is also worth noting that the early work on this problem was tied to some of the important early work that moved theory from evolutionary biology over to economics. The economists have been playing with this kind of theory … called game theory … ever since.

An interesting paper representing the overlap between economics and evolutionary biology with respect to this issue is “Economic man and selfish genes: the implications of group selection for economic valuation and policy.” From the abstract:

A basic tenet of socio-economics is that economic behavior is shaped by social bonds and cultural context. A relevant controversy in evolutionary biology is group selection and the related issue of altruistic behavior, that is, behavior neutral or detrimental to the individual but positive for the survival of the group. In this paper we examine the parallel controversies surrounding “economic man” and “selfish genes” with particular emphasis on the policy implications of group selection. We argue for the replacement of standard welfare economics with models of human behavior in the spirit of “consilience” between economic theory and the best available science from other relevant disciplines.

(Source:Gowdy, J. (2004). Economic man and selfish genes: the implications of group selection for economic valuation and policy Journal of Socio-Economics, 33 (3), 343-358 DOI: 10.1016/j.socec.2003.12.026)

As promised, here are a few suggested readings that will cover this topic (and other topics). Most of these are available used.

Genes in Conflict: The Biology of Selfish Genetic Elements

The Selfish Gene: 30th Anniversary Edition–with a new Introduction by the Author

Sex, Evolution and Behavior

Homicide (Foundations of Human Behavior)

Social Evolution

Natural Selection and Social Theory: Selected Papers of Robert Trivers (Evolution and Cognition Series)

More Falsehoods !!!

This post is one of a series on the topic of falsehoods. The following is a list of falsehoods posts in order:

• The Falsehoods
• “False Pearls before Real Swine”
• Falsehood: A baby is not the biological offspring of its adoptive mother
• Falsehoods: Has evolution stopped for humans?
• Natural Selection is Survival Of the Fittest (A Falsehood)
• Falsehood: Nature maintains balance.
• Is it a Falsehood that Humans Evolve from Apes?
• The poor and the dark skinned have more babies than the rich and the light skinned
• Acting for the survival of the species (a falsehood)
• Culture Overrides Biology (Another falsehood)
• What is the Placebo Effect, and it it getting stronger?

We sense that these are good because they are “threes” and “three” is a magic number. Here, I’m focusing on the Mode Trichotomy, and asking that we consider that there are not three, but four modes of Natural Selection. This will cause tremors throughout the Evolutionary Theory community because Four is not a magic number, but so be it.

In Stabilizing Selection the extremes of a trait are selected against and the mean value of the trait remains the same. Mutations constantly introduced into the population tht produce traits out at the extremes are selected against. In Directional Selection the values of a trait at one end of the distribution are selected against and/or values at the other end are selected for, so that the distribution of values, and it’s mean, move in one direction. In Disruptive Selection the average values are selected against so that the distribution of the trait becomes bimodal.

That was pretty simple, but operationalizing these definitions, displaying them graphically, and thinking about how they work in shaping the overall pattern of evolution reveal important details that are often sidelined or not discussed. And, we have to consider the fourth mode: Null Selection: This is where there is no selection on the trait at any particular value. As mutations (or allelic novelty of any source) are introduced into the population what might have been a nice bell curve representing the trait’s values spreads and flattens.

One might argue that since “Null Selection” is not really selection, that it should not be a mode. I agree, but I still want it on the list of modes of selection. Why? Because without a concept of null selection, the lack of change in trait values is often incorrectly interpreted as “nothing is happening here.” But in fact, something fairly major and impressive is happening. Stabilizing selection is the process of ongoing introduction of variation and ongoing reduction in variation. It balances out because the more introduction of variation there is, the stronger selection becomes. A trait that remains the same for eons is a trait experiencing a dynamic evolutionary processes. Having no concept of Null Selection does not allow this thought to develop, or if it is mentioned, it may not stick as well.

Below I provide graphics depicting the modes. (They are available for non commercial use. For commercial use, that’s $1,000 Euros each. Oh, and click on the graphic to get a larger version.) I’ve made the graphics very simple but they are also meant to be very precise in selected details. as described below in the text.

Stabilizing Selection

As stated above, stabilizing selection occurs when the “central” value of a trait is not selected against or favored by selection but extreme values are selected against. The graphic shows “selection against” only, and this is depicted as rather menacing looking arrows pointing down at the upper and lower reaches of this “bell curve” shaped distribution. Note that the “after selection” graph shows that the extreme values from before selection are gone, the total range of variation is lower, and the mean is unchanged.

Directional Selection

Here the nasty looking Force of Selection Arrow is only affecting traits near one end of the distribution. The entire distribution squishes to the right. Note that the upper end of the distribution does not move up … in other words, directional selection does not simply move the bell curve along in one direction. The total range of variation reduces and the mean moves, in this case, to the right.

Disruptive Selection

In this case the central or average value is being selected against and/or the extremes selected for. My favorite example of this, and one often given in the textbooks, is the selection for gamete size. Fitness may be enhanced with a gamete with a certain amount of nutrition stored for use in a growing zygote (seed or embryo). Or, fitness may be enhanced by a small lightweight and mobile gamete (a pollen spore or a sperm). You can’t have both, and the compromise is less than ideal. [see this on Anisogamy] This example also forces us to realize that fitness needs to be considered in relation to the morph … the individual as it exists with a certain gender, developmental age, etc. Monty Python and the Catholic Church notwithstanding, a sperm is an individual with it’s own little genome and it’s own little Darwinian problems. So is an egg or a spore. They don’t have a lot of personality but they do have a fitness function.

Those are the usual three forms of selection, and the one I want to add is “Null Selection.” Is this the same as “relaxed selection” you may ask? If you want it to be that’s OK. Neither have definitions that are both formal and accepted. They are probably the same.

In null selection there are no Arrows of Selection happening to the bell curve, but there is still the constant introduction of mutations, so over time the distribution goes wacky and essentially becomes random.

For this to be really clearly conceptualized, we can go back to Stabilizing Selection and redraw the diagram like this:

Here, the mutations are seen constantly bothering the bell curve from below, and selection is working in an uneven way (more against the extremes) in the opposite direction. In cases where people have actually measured a trait over time, one sees this dynamic process. This is the equilibrium in punctuated equilibrium.

But this question is a falsehood at another level. In reality, there are two additional questions that are actually being asked when this question is brought up:

• Aren’t humans no longer subject to natural selection?; and
• Aren’t humans not likely to give rise to a new species?

The first assertion is a widely held belief with absolutely no foundation, so it qualifies as a true Falsehood. The second question is not so widely discussed. Here, we’ll focus on the first and leave the second for another time.

Are human beings “still” subject to natural selection? This is a loaded question: Loaded with tricky words like “are” and “still” and “selection” and “human being.”

Let’s start with the Are-Still problem. A species is an entity that has temporal (time) and spatial (geography) dimensions. So an expanding population/species covers more and more geography over time, and so on. The “Are-Still” part of this question must be referring to some part of that time-space continuum. I think what is usually meant by “humans” is humans in this modern world of medicine and dominance over the environment, etc. In particular, it means humans as a population not subject to scarcities of food, ravages of predation, and suffering by disease. This is because in many people’s minds evolution roughly equals natural selection and its effects, and natural selection roughly equals these listed aspects of the environment and their effects. The struggle for existence, the competition for food, and so on. And the struggle is over. (Remember, we’re talking Fallacies here … )

The other biggie, sexual selection, is often left out of the discussion. The popular mindset often seems to lack a concept of human mate competition or mate choice as factors in human evolution or human affairs in general. I think this is due to modern conceptions of monogamy. We fool ourselves into thinking that since there is the same number of men and women. and everybody eventually gets married to a member of the opposite sex, etc. , then there really is no mating competition or sexual selection. (Not true, not true, and not true.) This is a deeply fascinating set of assertions, beliefs, fallacies, and innuendos. Almost everything in evolution is about food and sex. But let’s deal with the food first, and save the sex for later. (Always a good plan.)

So “Are-Still” part of this fallacy addresses a particular temporal-spatial chunk of “Human Beings.” What about selection? Here the very simple (and meaningful but nowhere complete) answer is this: If we have removed with modern medicine, agriculture, and deadly weapons the parasites, predators, and food limitations from our environment, that does not mean that we are not evolving. What it means is that a large number of selective forces have shifted. Since we are talking mainly about stabilizing selection related to the ability to find food, avoid predators, etc. (maybe some directional selection as well), this mostly means that we are experiencing “relaxed selection.” This is when selective forces that were there are no longer there (relaxed).

Many people confuse this with “not evolving.” But remember our earlier discussion. “Evolution is change in allele frequency over time.” And remember that mutations are common, and that most of them are weeded out. So relaxing selection almost always has to result in increased rates of evolution. So not only are humans not “not” evolving, human evolution may be accelerated in some areas of the genome. What a time to be alive!

But there is, as you may already be thinking, another big problem with this. The “Are-Still” construct in combination with the environment being less “red in tooth and claw,” and all that, is problematic. And here we are going to get to the part of this discussion where many people will get mad at me. Sorry, but the assertion that we are not evolving because we have solved all of these problems is racist, classist, and Westernist. You are a bad person for thinking these things. But that’s OK, we still love you and you can change.

Different human populations are very closely related to each other, reflecting both recent separation of those populations and long term flow of genes across populations that believe falsely themselves to be separate. There are people right now living in some far off part of the world, whom you’ve never heard of (nor they of you) who are among the most genetically distant from you right now, among whom are individuals who’s great great great great grandson or granddaughter are going to have sex with your great great great granddaughter or grandson and thusly produce offspring. How do I know that? Because I traveled way back in time in an imaginary time machine I keep around for thought experiments, and made that prediction 100 years ago, 1000 years ago, 10,000 years ago, and 30,000 years ago and every time I was correct.

The modern human genome is fluid, it has been fluid for tens of thousands of years, and it will be fluid for whatever future exists until either the sun explodes or somebody really screws up and sends us into extinction.

Right now, as I’m sure you know, a huge part of the earth’s population of humans does not have protection by modern wonders of science from parasites. A lot of people in Uganda are eaten by lions each year. People often starve. In other words, the usual selective forces are very much at work in our species, somewhere, indeed, in many places. Many different forces of selection are at work to differing degrees in different parts of the world and at different times (leading to genetic diversification?) and gene flow is ongoing across the planet (leading to genetic variability that defies sub speciation?)

It was possible, maybe, 25 years ago or so, to incorrectly but convincingly hold up Western Culture and Civilization as the place/time where many of the environmental forces of selection have been reduced. However, more and more people each year living in Western Civilization are less protected because of increase poverty and a widening gap between the “haves” and the “have nots.” On top of that, some of the ravages of nature that we thought we were protecting ourselves from (like bacteria and viruses) are co-evolving with our defenses. And, presumably, or defenses are co-evolving as well. Yet another factor is the novelty of the environment. Some populations may have gotten out of being eaten by lions or running out of food, at least for the time being. But these populations have likely run into other problems. Obesity results in morbidity and mortality and may affect fertility or reproductive success in various ways. Obesity is growing to an epidemic in the US right now. Obesity as a consistent feature starting in childhood will certainly have selective effects. How can it not?

There are probably dozens of effects of “civilization” that have their own selective stories. So Natural Selection is still very much at work in the usual ways. Natural Selection in some areas is relaxed, thus changing evolutionary rates and trends, and not by any means eliminating them. And Natural Selection is working in relatively novel ways through the effects of changes in the environment caused by modernization.

So… Hypothesis: “Human beings are no longer subject to Natural Selection.”

Falsehood Falsified.

More Falsehoods !!!

This post is one of a series on the topic of falsehoods. The following is a list of falsehoods posts in order:

• The Falsehoods
• “False Pearls before Real Swine”
• Falsehood: A baby is not the biological offspring of its adoptive mother
• Falsehoods: Has evolution stopped for humans?
• Natural Selection is Survival Of the Fittest (A Falsehood)
• Falsehood: Nature maintains balance.
• Is it a Falsehood that Humans Evolve from Apes?
• The poor and the dark skinned have more babies than the rich and the light skinned
• Acting for the survival of the species (a falsehood)
• Culture Overrides Biology (Another falsehood)
• What is the Placebo Effect, and it it getting stronger?

Let’s use the term “naturalistic” to mean the assumption that what we observe in nature is the optimal, correct, or “best” approach to doing something. That which we observe in nature is the best guide to how things should be. We can see that in mammals mothers nurse their young. Departures from this (bottle feeding, early weening, feeding young something other than mother’s milk, etc.) are risky and typically have negative consequences. Humans in a “state of nature” (such as hunter gatherers) get a moderate but regular amount of exercise in carrying out their day to day business compared to humans in a “state of suburbia” who can get their stuff done with almost no physical movement. Human foragers are trim and fit, human suburbanites tend towards heart disease. This suggests that regular moderate exercise is good, and both scientific research and experience seem to support this.

So far so good. A “naturalistic assumption” seems the way to go.

In the Western industrialized world, we have a widely held concept of what is “natural” and we tend to make a link between “natural” and “good.” We tend to ‘believe’ in a socially constructed balance between natural and non natural choices. However, we also possess other beliefs and priorities that sometimes conflict with the naturalistic assumption. For example, a child that is fatally allergic to mother’s milk would be left to die with a pure naturalistic philosophy. However, the life of such a child is typically valued more highly than one’s philosophical purity, and non-natural intervention (feeding the child soy milk from a bottle) is chosen as the ‘correct’ decision. In truth, day to day, we are utterly arbitrary in adherence to or ignorance (willful or otherwise) of the naturalistic premise. We do what is convenient, what feels good, what provides us some perceived good or benefit (money, status, etc.). Then later we explain our decision rhetorically as necessary, and sometimes the naturalistic premise is invoked.

Naturalistic perspectives are often invoked when considering political or economic decisions. Free market capitalism is natural. Competition is natural.

Let’s look more closely at one of the often cited examples of using a naturalistic premise to justify a social or economic reality which is rather controversial: The well documented fact that women get paid less than men in Western society.

There is plenty of room for clarification here … do women get paid less than men for the same exact job? Do women get paid the same but end up with a lower salary because they take unpaid leave to have babies? Do women get paid the same but end up with lower pay because they take unpaid leave which indirectly contributes to slower (in calendar time) advancement on the pay scale? Are women kept out of jobs, or even entire professions, that tend to be higher paid? Some or all of the above?

I’ve collected a list of phrases that are typical of the naturalistic assumption being applied to the question of salary, paraphrased from comments over a period of time made on my blog. The purpose of this list is to provide an evidence based description of what people are saying about women’s salary.

• Is every difference in how we treat males vs. females insulting? Why stop at lower salary for women? What about holding the door for the weaker sex? What about getting to improve one’s daily look with make-up being the exclusive right of women? Why should men, the stronger sex, always carry all the groceries?
• Is paying women and men the same salary really fair? The two sexes are different, having different strengths and advantages, and are limited in different ways. Those differences justify the fact that salaries are skewed.
• … from an evolutionary point of view it is more important for men than for women to earn money, as money is earned for status, and not for consumption.
• Psychologically, men are more aggressive, more ambitious, and more authoritative. They are more often psychopathic, and generally less caring of others …
• …being more aggressive and ambitious, more authoritative and psychopathic, less caring of others are “qualities” that are sought by corporations seeking high-end CEOs…
• …hiring a woman results in the risk that she will be unable to work if she gets pregnant. The “worth” of that employee is thus reduced.
• …in divorces it is the wife who gets the children. …. it is reasonable to consider the higher salary of men as a compensation for that.
• Clearly, the salary difference has a biological basis. Until it is thoroughly understood why this biological difference exists it is wrong to say that it should be abandoned.

Is there something to these comments? Is there a way to not just explain, but actually justify our social and cultural rules and behaviors from a naturalistic premise?

A naturalistic basis for determining what is proper or justified in human behavior may take into account the fact that we are mammals. Our mammalness, as part of our broader “animalness” encompasses many of the critically important facets of our lives. We have two sexes, a male (producing sperm) and a female (producing ova). Pregnancy lasts a long time relative to the overall life cycle of a given female, so baby-making is a big investment and any risks or costs associated with this endeavor are large. The females nurse the young, adding significant time and energy in the form of child care. In mammals, males typically fight or display for sexual access, and females are either herded or harassed by males or choose males with which to mate, and males provide virtually no offspring care in most species. In some species there is courting and female choice, in others, hormonally mediated sexual arousal and activity, in others, what we might call rape.

That is a pretty wide range of behaviors, but one must use this wide range to describe ‘typical’ mammals, as they do vary. There are key characteristics that do pertain to all mammals, however: Pregnancy and nursing being entirely female, longish period of offspring care, and internal fertilization which results in a certain amount of paternal uncertainty (unclear attribution of fatherhood) for all males.

Given this, we may expect human males to be less choosy (sexually) than females, we may expect males to be promiscuous, we may expect females to be more cautious, we may expect males to be show-offs and often more violent than females, and we may expect males to be bigger and stronger than females. Given this, perhaps we can begin to explain human males’ attention to sports, and shopping behaviors found among females. Perhaps we can even justify certain human behaviors. Violence, for instance. Indeed, there are historically documented legal systems that would punish a woman severely for the murder of her husband’s illicit lover, but punish the man much less severely for killing his wife’s illicit lover.

But wait, there’s more. We are mammals but we are also primates, which is a subset of mammals. Would it not be more appropriate to look to primates, rather than mammals more broadly, for our fundamental naturalistic natures?

Well, most primates are either solitary or monogamous, with males and females not differing very much in size. Mating happens as a matter of female choice more than male-male tournament competition in most primate species. In many primate species, especially the polyandrous ones (where a single female has two or more male mates) there is a certain amount of male care of offspring, while in others, not so much. There is almost no difference in the potential effectiveness of fighting anatomy (such as canines) in males vs. females in most primates.

So, our evolutionary heritage as primates actually looks quite different than if we look more broadly at mammals. We might expect male humans to track females very carefully, be more or less at their service with respect to child care, and we should see very little difference between the sexes in who gets to use force or coercion for personal gain. Males and females would roughly share the job of protecting home and hearth (proverbially or otherwise). Males in many cases would not know if they are the father of a particular female’s offspring, but they would remain devoted to the female and her young because the young are related in some way. The multiple males hooked up to individual females would typically be half brothers, for instance.

But really, while we are in fact primates, we are actually Old World Primates. If we remove the prosimians and the New World Primates from the mix, and look only at Old World ‘higher’ primates, we get a different picture. In this comparison, we actually drop all of the polyandry and most of the monogamy. We now get a pretty large difference, on average, in body size of males vs. females, but male coercion is rarely a means of sexual interaction … rather, females and males both engage in quite a bit of politics (these are smart animals) and these political interactions are mediated by quite a bit of biting and poking (within both males and females, but maybe more so in males). The result is often a parallel (male vs. female) set of hierarchies, and position in these hierarchies determines for males who gets to mate and for females who ends up most successfully raising offspring.

From this perhaps we can still understand such human behaviors as guys getting together to do sports and gals getting together to shop and compete over makeup and shoes, and we get to explain politicians and People Magazine as well! Gossip, politics, personal status, etc. are all expectable pastimes or passions from such an Old World Primate ancestry. When we look at a modern politician, we can often imagine a baboon. When we read a popular culture magazine, we may be reminded of that troop of Japanese macaques we saw last week at the zoo. Now, we’re really getting somewhere!

But wait, the Old World Primates split into diverse evolutionary branches a VERY long time ago. Maybe we should look at the subset of Old World Primates of which we are a part … the apes.

The majority of ape species are monomorphic in body size (the males and females are the same size) and practice life-long pair bonding. Both males and females are physically equipped (strong bodies, big canines) to defend the territory and the young, and both take similar roles in this regard, though the females nurse the young so there is some difference in male vs. female role in offspring care. A considerable effort is put into care of offspring overall, and with setting them up in new territories, etc., and this sort of care involves the males at least as much as the females.

So we might expect humans, as apes, to be highly monogamous and to put huge amounts of efforts into offspring … somewhat different in style but with similar levels of effort for males vs. females.

But hold on a second there… we are apes, yes, and this characterizes the average ape because gibbons and siamangs are all apes and most apes are gibbons or siamangs, if we just count the number of species. But they are so-called “lesser apes” and we are so-called “great apes!” The great apes constitutes a smaller taxonomic group. Maybe we should look at the great apes only and forget the gibbons and siamangs.

OK, when we do that, we are looking at orangs, gorillas, chimps, and bonobos. Orangs have a very high level of sexual dimorphism, are primarily vegetarian, and the most typical form of sexual interaction is either forced copulation (akin to rape) or females swooning over gigantic, and presumably very sexy, but rare, super males. All offspring care is provided by the female. In fact, the largest social group among these apes is the mother and offspring with a random male busy raping the female while the offspring hangs out on a nearby branch eating some wild figs. Gorillas also have a high level of dimorphism in body size, but live in large groups with the key group structure consisting of a silver back male and a harem of females who are totally devoted to and sexually monogamous with the male until a lone silver back shows up and starts to kill the female’s infant offspring now and then. When that happens, the females join the infanticidal male and abandon their devotion to the original silver back.

These two apes provide very different models, but are similar in that females are either raped or have their “children” killed (and they can stop that by joining the killer) and when push comes to shove, the enormously large males get to do all the pushing. This would suggest that humans get comfortable with a very male dominated society and that the females should just get in line. Fast.

But hold on, we are much much more closely related to the chimpanzees. We are equally related to each of the two chimpanzee species, common chimps and bonobos. So let’s look at their lifestyle.

Both groups have the unusual and interesting feature of multiple adult sexually mature males and females living in the same group. When a female is in a state of ovulation, she also enters a state of estrus … the visible display of ovulation. Some of the males may be forced to not mate with this female (forced by dominant males or coalitions of males) but for the most part every male mates with such a female at some point. Over time, all of the females go into estrus one or two at a time. So, over the course of several years, every single male will eventually have potentially baby-making sex with every single female. This is done in the form of giant orgies in which only one female participates.

That is true for common chimps, but it is also true for bonobos, with an added twist. All the chimps have lots of what I will call erotic interaction all the time, including auto erotic. But for bonobos, there is the added feature of almost every possible gender and age combination of non-baby making erotic interaction, and every combination of body part interaction. So a young female may provide oral sex to an older male. An older male may provide oral sex to a young male. Two adult females may engage in genital-genital rubbing. And so on and so forth. Over and over again. OMG.

Young males do not seem to have sex with their mothers. Otherwise, pretty much every combination of erotic interaction can and does happen.

So, given the chimp model, we should all be bisexual and disregard age or gender of our sexual partners. Almost all baby making sex should involve a gang bang lasting several days. We should have strong male hierarchies and female hierarchies that determine, ultimately, who gets to be the father of each child (more or less) not by who has sex with whom, but by regulating exactly when in the ovulatory cycle intromissive sex with male orgasm happens. If we lean towards the common chimp model, all males should be dominant over all females. If we lean towards the bonobo model, all females should be dominant over all males. And somehow, from this, we have to explain human female shopping behavior and sports.

So, that is the sum of our naturalistic models … where they come from and how we might use them … assuming that our evolutionary heritage, our phylogenetic framework, our Darwinian determinism, should provide us with the best naturalistic guidance for day to day behavior.

But hold on one more time: There is another thing we should think about in building our naturalistic model: Birds.

We might be mammals, but we act like birds. Like chimps, we exist in societies with multiple potentially sexually mature males and females. But we tend to pair bond (or nearly so) within this framework. In this sense, we are very different than our closest living mammal relatives (who, by the way, are relatively very distant in relationship compared to many other pairs of species!). We are not that closely related to birds, but if we look at a wide range of human societies known to live off the land (‘preagricultural’ groups, either in the present or ethnohistorically known), we see that human societies are often very close to bird societies. We have some kind of monogamy that occasionally develops into a bit of polyandry (like traditional Tibetan highland groups and the phalarope birds of the arctic) or a bit of polygyny (like many cattle keeping groups or the oft-studied oft-cited red winged blackbirds and many other birds). But even in societies that do allow polygyny, most families are based on monogamy, though it is serial monogamy (like the vast majority of bird species including almost all song birds).

Yet, when certain economic features … like land (nesting sites) and professional or social milieu (territories) are essential to status and wealth, we have very long term monogamous systems in humans such as the immutable Christian Victorian marriage (or in birds the life long bonding of raptors). In all birds, there is a LOT of care invested in offspring, and males and females deliver similar levels … and in some species very similar kinds … of this care. In humans, there is also considerable care in offspring but … alas … we are mammals so females don’t lay eggs (allowing for male investment at an early stage) and males can’t nurse the young. This starts a cascade of male-female differences. Perhaps females care for the young directly while the males busy themselves defending the territory.

Why, it is rather remarkable how birds map human variation in society in so many ways. But not all. Birds rarely live in tightly knit, spatially close groups of sexually active pairs. One example of this is nesting sea birds like gulls and terns. And for gulls and terns, the biggest survival risk in early life is that your neighbor eats you while your parents are distracted. There are certainly human analogs to this (infanticide is a real factor in shaping human society) but the parallel is weak.

Dear reader, if you are still with me (and I would understand if you’ve gotten bored or frustrated and gone away by now) then you can easily see this point: We have a rich supply of models from which we can draw naturalistic conclusions, and these models can be used to ‘justify’ or explain almost anything. This makes them lousy models, unless you are in the business of just making stuff up.

A better approach might be to ask: What is the premise we choose, as a society, to be the basis of our ethical and moral codes, our laws, etc.? For many people, this premise is mutualism. We agree to equality of all individuals (with special exceptions). This equality does not mean individuals are identical. Indeed, there may be categorical differences among groups. Females do have babies, males do not. But equal rights are to be preserved. Then on the basis of this equality, we agree to interact in positive, mutually beneficial ways. One hand washes the other. What goes around comes around. We watch, and occasionally scratch, each other’s backs. Friendship, camaraderie, and civility are valued practices.

This does not mean that the naturalistic consideration goes away. What it should mean is that naturalistic models can not be used to justify systematic social, cultural, legal, economic, philosophical, or political inequalities. But they can be used, if used properly (and that is an academic, not political issue), to explain some things. Even so, most of the explanations we encounter in the popular literature are selective, unjustified, inappropriate and poorly executed. In my opinion, we are very very far from being able to explain much with what we currently know, and certainly not at the pop psychology level seen in the comments cited above.

But I do want to make an attempt at a naturalistic consideration of modern human society with respect to two realities. One, females have the babies and males do not, and two, males tend to be more violent and aggressive than females.

The fundamental reality of these propositions needs to be tested first. Do the females really have the babies, and what does this mean? Well, it is not so simple. For the most part, females do have the babies but with modern approaches it is possible and indeed quite common, and in some cases, necessary, for males to have much more input in offspring care in humans than one might otherwise predict from a purely naturalistic model. For example … and very few people know this about me, and learning this is your reward for sticking with me this far along in this essay … I personally fed my daughter for her entire nursing period. I held her, I gave her the milk, we stared into each other’s eyes and bonded lovingly, the whole nine yards. Not her mother. Me. So, while the female clearly has a major biological commitment to the process, it is not as absolute as one might assume.

With respect to male violence and aggression, remember what Margaret Mead said. Mead claimed that there were societies in which females were more aggressive or violent than males, and thus, the whole male aggression thing was a pure cultural construct. Well, Mead was a great person and a great anthropologist, but she was wrong about that. There are no such societies. On the other hand, and in anthropology there is always another hand, Mead was not totally wrong.

Yes, males are always, without exception, more violent and aggressive, on average (and bigger and stronger too) than the females within a given society. But the absolute level of aggression and violence among both males and females is highly variable. Therefore, there can be females in one society who are more violent and aggressive than the males in another society. Most importantly, the level of difference between males and females in a given society … and especially the level of male control over females … varies greatly. There are societies in which there is very little difference between males and females, and there are societies in which the difference is great. Americans: You live in a society where the difference is considerable, more than the average. That is not how it has to be.

So, with respect to our individual selfish Darwinian reproductive goals, our broader social (territorial, economic, etc.) goals, and our cultural fixations, babies and aggression are both important. Offspring are our Darwinian legacy; sons are guns; little girls grow up and give their parents more Darwins (a unit of fitness) by helping raise more children and by having babies of their own. Sexual access must be ensured and paternity managed. Territory must be held, resources protected. And so on.

The problem is that only the ladies can have the babies, and it mainly falls to the gents to be the tough guys. On top of this, when a woman has a child she may fall short in some other responsibilities such as carrying all the firewood and water and other physically demanding tasks (as occur in most societies where women do the vast majority of hard labor). For their part, this aggressiveness of males comes in handy for defending the group territory, but it often becomes a nuisance and becomes a very serious problem when this aggression turns to beating, raping, murdering, and threatening others, mainly women.

So how do we deal with this? Start out by admitting that we as a society owe women a great deal for being the baby bearers. It is hard, painful, and you can die doing it. But no. In our society, we take away a woman’s rights because she is the baby bearer. She is paid less, and as one of the comments cited above suggests, her value is diminished.

• “…hiring a woman results in the risk that she will be unable to work if she gets pregnant. The “worth” of that employee is thus reduced….”

We also deal with this by admitting that aggressive male approaches are not necessarily a good thing. Yes, it may be true that men earn money in part for status, and not for consumption, but that would be because men are being assholes. If it is true that being aggressive, ambitious, authoritative, less caring and even psychopathic are ‘qualities’ that are sought in CEOs, then we have to stop doing that. We have to stop seeking and rewarding those qualities.

Compensation works both ways. We must compensate, as a society, for the burden of our evolutionary past as manifest differentially by gender. Our behavior is flexible, and thus it is incumbent on our society to attenuate violent leanings. Childbearing is fundamental and essential but cannot be totally outsourced by the women who do it. Punishing women for having this responsibility is exactly the opposite of what we should do.

A review of our evolutionary context is interesting to me (it is what my professional research life is largely about) and this context is causative. But a realistic look at our evolutionary biology does not give any simple answers, and never, ever does it provide justification for unfairness or violence.

There is a reason they call it the Naturalistic Fallacy.

¹The entire conversation related to the evolutionary context of modern human health and behavior can be researched by beginning with the work of Eaton, Konner and Shostack and working backwards and forwards from there. Here are two of the key references to get your started.

S Eaton (2003). An evolutionary perspective on human physical activity: implications for health Comparative Biochemistry and Physiology – Part A: Molecular & Integrative Physiology, 136 (1), 153-159 DOI: 10.1016/S1095-6433(03)00208-3

Eaton, S. Boyd, Konner, Melvin (1985). Paleolithic nutrition: A Consideration of its nature and current implications. New England Journal of Medicine, 312 (5), 283-289

DNA can mutate and change imperceptibly every time a cell divides and makes a copy of itself.

But when one of these mutations causes a change that is advantageous for the animal – for example, rendering it resistant to a particular disease – it is often “selected for”, or passed down to the next few generations of that same species.

Such changes, which create differences within a population but do not give rise to new species, are known as “microevolution”.

I suppose the BBC is into the Hopeful Monster theory or something.

Read it here, come back, and fight it out.

There are several possible explanations for this….

…The most important one might be that this sort of behavior doesn’t really happen very often. It is so rare that it can be ignored and written off as irrelevant in the light of overwhelming evidence that humans usually act selfishly. There are billions of people in this world, but we can name the top altruists. We can’t name all the selfish people.

But if we want to provide a hypothesis that could explain non-kin based altruism that should be kin-based altruism, there is one.

We don’t need to explain altruism as kin-based. One person can do something “altruistic” for another person because they expect (and usually get) a return, like in that move that I haven’t seen “Pay it forward” or that insurance company commercial that I’ve seen too many times (not the cavemen or the gecko, but the one where the lady stops the man from getting run over, etc.). More likely, such forms of reciprocal altruism are more direct. I scratch your back, and in the not too distant future, you scratch my back (not someone else’s back).

We may also expect “altruistic acts” to occur as a means of showing off.

But the burning baby and hand grenade scenarios don’t involve a payoff if, at the end, you are dead. So, these behaviors have to be either truly dumb from a Darwinian perspective, or something else.

This is where Ultimate vs. Proximate explanations or mechanisms for behavior come in. Simply put, an organism may be selected by Darwinian processes to tend towards a particular behavior, and in the context of this behavior’s evolution, it makes sense to implement this behavior under certain conditions. But then the conditions change. When the conditions change, evolution may eventually cause a change in how this behavior works, but in the meantime the behavior becomes (at least some times) “inappropriate.”

Since there is a difference between the ultimate (evolutionary) fitness-related reasons for the behaviors existence and the specific neurological or hormonal mechanism for the behavior’s implementation, the former can make sense in the large view, and the latter often not make sense in the immediate instance.

In the so-called “environment of evolutionary adaptiveness” men are usually with other men who are their close relatives. In humans, it is more often than not the female who moves out of her natal (birth) group to join her new mate in his natal group. Thus, a given man is related to the other men in his group. The other men may include his father, uncles, brothers, and sons. Children in the group are all his children, his siblings children, or otherwise related. Thus, at any one moment in time, if you can give up your life to save every single person in you group, you might be doing something that makes sens in an evolutionary framework. At the very least, there should evolve a mechanism that allows for the option of suicidal altruism.

The guy in the army is not hanging around with his relatives. He is unrelated to his fellow soldiers. But in the evolution of this trait, there did not develop a mechanism to assess this degree of relatedness to group members. The degree of relatedness was an already extant, expected, reliable thing that made up part of the context in which suicidal altruism might evolve. Perhaps all it takes is a sense of “brotherhood” to cause a male’s brain to shift into “might-have-to-die-to-save-genes” mode. Certanily, training, living, and fighting together could facilitate this sense of brotherhood among men in the military, and it is clear (and this has been studied) that there are training techniques and other aspects of military life that enhance this phenomenon.

Thus, evolved traits including behaviors always have to be understood … explained … at multiple levels. One way to do this is to separately consider the ultimate (evolved, fitness-related) and the proximate (mechanistic … how does the trait actually work) levels as separate. (There are other levels but that is for another time.) The proximate mechanisms can be very powerful. Hunger and sex drive. Say no more.

This way of thinking helps to explain the very interesting behavior recently exhibited by a pair of gay flamingos. (Thanks to CMF for bringing this to my attention.) Gay flamingos may seem odd, but there are gay couples (both males and females) in all thus-far studies species of pair bonding birds.

Here’s the story:

LONDON (AFP) – A pair of gay flamingos have adopted an abandoned chick, becoming parents after being together for six years, a British conservation organisation said Monday.

Carlos and Fernando had been desperate to start a family, even chasing other flamingos from their nests to take over their eggs at the Wildfowl and Wetlands Trust (WWT) in Slimbridge near Bristol.
But their egg-sitting prowess made them the top choice for taking an unhatched egg under their wings when one of the Greater Flamingo nests was abandoned.

The couple, together for six years, can feed chicks by producing milk in their throats.
Fernando and Carlos are a same sex couple who have been known to steal other flamingos’ eggs by chasing them off their nest because they wanted to rear them themselves,” said WWT spokeswoman Jane Waghorn.

“They were rather good at sitting on eggs and hatching them so last week, when a nest was abandoned, it seemed like a good idea to make them surrogate parents.”
Gay flamingos are not uncommon, she added.

“If there aren’t enough females or they don’t hit it off with them, they will pair off with other males,” she said.

Both male and female birds in pair bonding species tend to have strong nesting and off-spring care drives. These drives are hormonally driven (that’s the proximate mechanism) and serve to enhance individual fitness by enhancing reproductive success (that’s the ultimate explanation). It has been noted that gay male couples seem to do a much better job at raising young than heterosexual couples (and possibly gay female couples) in birds. I suspect there could be two reasons for this, if it is true. First, males may need extra doses of offspring care hormonally mediated drives in order to get them to do the right thing (instead of acting like guys). Second, they may be engaged in less intrasexual competition, and thus have more energy and time for offspring care.

(By the way, there is a famous pair of gay male eagles at the US National Zoo that has raised many offspring from eggs laid by hetero-birds.)

It probably helps that in Flamingos and many other birds, males can “lactate.”

A recent paper in PNAS addresses the size difference between fresh water and marine diatoms. Cell size is potentially a very important variable for these little organisms. For instance, larger cells would, on average, sink more frequently and quickly to the bottom of the ocean, thus sequestering carbon (this carbon is the carbon in the living tissue of the diatom). There are presumably ecological reasons why larger vs. smaller cells would evolve.

It turns out that the size range is greater and the maximum size is larger in marine diatoms compared to fresh water diatoms. Why?

The study considered the role of Nitrogen vs. Phosphorus limitation on cell size. Nitrogen and Phosphorus have different patterns of availability in marine vs. fresh water settings. Nitrogen is probably more of a limiting factor in marine environments, and Phosphorus is probably more of a limiting environment in fresh water environments. Also, the range of depths at which diatoms can survive for longish periods of time is greater in marine environments than it is in fresh water environments. For various reasons, both of these relationships suggest that larger diatoms would do well in marine environments.

When Nitrogen is abundant and consistent, fast growth rates of cells is possible. Whenever it is possible, we expect fast growth rate of tiny organisms to be selected for (unless there is some counteracting effect) because in this way the organisms can grow out of the size range for at least some of their predators. The faster rate of growth leads to smaller maximum size.

Although Nitrogen can be limiting in marine environments, it is also very variable in amount over time Variation in the basic food supply for any orgasm can lead, other things being equal, to smaller body size for space limited creatures like elephants on islands, but for these single celled organisms, variation in body size leads to larger size because of the greater potential for food storage in the larger cells.

Another factor is the importance of sinking. For a diatom, sinking too much = death because these organisms get their energy from sunlight. Physiologically active diatoms don’t sink, but when the cell becomes inactive it may start to sink. In diatoms that are physiologically active (healthy, there’s enough sunlight, etc.) size does not affect sinking rages, but in cells that are less active owing to lack of nutrients or sunlight sinking is quicker in larger cells. However, really large diatoms actually sink more slowly than small ones. Therefore, variation in physiological activity selects for a greater range in diatom size. This is what is probably happening, in part, in marine settings.

In contrast to the situation with Nitrogen, variation in Phosphorus seems to select for small sized diatoms, for reasons that are not entirely clear (so we’ll just skip that part…)

The present study gathered data on diatoms and their environments from a wide range of sources, then used all of these data to run simulation studies testing various ESS strategies. The ESS simulations significnatly refined the understanding of diatom evolution and confirmed and provided detail to the idea that Nitrogen and Phosphorus levels, as well as the effective depth at which diatoms operate, explain through Natural Selection theory what we see in nature.

ESS stands for Evolutionary Stable Strategy. This is an interesting and important concept in evolutionary theory. A strategy is pretty much anything that can be thought of adaptively. Body size is a strategy, a certain foraging pattern may be a strategy, etc. A stable strategy is a strategy that is held in place, such that alternative variants are somehow avoided, over time. An Evolutionary Stable Strategy is one in which Natural Selection has in a sense “chosen” among a set of alternative strategies the one strategy that out does all others with respect to fitness. This strategy … this ESS … is expected to remain as the dominant, in place strategy forever. Or until a new ESS comes along, invading the population and replacing the original strategy. Since evolution works with random mutations as the starting point, the “One True ESS” may not be extant in a given population, but then, when it emerges it should spread. In truth, however, since there are lots of mutations and lots of time, most strategies in most populations are already The One True ESS or close to it. What can happen over time, however, is that conditions change and what once was The One True ESS is supplanted by a similar … but importantly different … strategy that was, in a sense, waiting int he wings as part of normal variation.

Litchman, E., Klausmeier, C.A., Yoshiyama, K. (2009). Contrasting size evolution in marine and freshwater diatoms
PNAS, Early Edition