Tag Archives: Genetics

The Three Necessary and Sufficient Conditions of Natural Selection

Natural Selection is the key creative force in evolution. Natural selection, together with specific histories of populations (species) and adaptations, is responsible for the design of organisms. Most people have some idea of what Natural Selection is. However, it is easy to make conceptual errors when thinking about this important force of nature. One way to improve how we think about a concept like this is to carefully exam its formal definition.

In this post, we will do the following:

  • Discuss historical and contextual aspects of the term “Natural Selection” in order to make clear exactly what it might mean (and not mean).
  • Provide what I feel is the best exact set of terms to use for these “three conditions,” because the words one uses are very important (there are probably some wrong ways to do it one would like to avoid).
  • Discuss why the terms should be put in a certain order (for pedagogical reasons, mainly) and how they relate and don’t related to each other.

When you are done reading this post you should be able to:

  • Make erudite and opaque comments to creationists that will get you points with your web friends.
  • Write really tricky Multiple Choice Exam Questions if you are a teacher.
  • Evolve more efficiently towards your ultimate goal because you will be more in control of the Random Evolutionary Process (only kidding on this third one…)

Continue reading The Three Necessary and Sufficient Conditions of Natural Selection

Is Human Behavior Genetic Or Learned?

Imagine that there is a trait observed among people that seems to occur more frequently in some families and not others. One might suspect that the trait is inherited genetically. Imagine researchers looking for the genetic underpinning of this trait and at first, not finding it. What might you conclude? It could be reasonable to conclude that the genetic underpinning of the trait is elusive, perhaps complicated with multiple genes, or that there is a non-genetic component, also not yet identified, that makes finding the genetic component harder. Eventually, you might assume, the gene will be found. Continue reading Is Human Behavior Genetic Or Learned?

A Possible Problem with CRISPR

Viruses use the DNA of their hosts to help themselves reproduce. Bacteria have counter-attacked viruses by grabbing some of the DNA from viruses and using this to identify them and kill them back. That as an oversimplified description of an eons old arms race between viruses and bacteria.

Among the DNA sequences co-opted by bacteria is the famous gene-frag-family known as CRISPR. You’ve heard of it, and you probably know what it does. Briefly, genetic scientists can use the innate power of CRISPR to manipulate other DNA to “repair” or modify in situ DNA sequences in living organisms. Got a genetic disease? No problem. We get the good genetic sequence, and then use the CRISPR based technology to replace all your bad DNA with the good DNA.

Now, of course, that doesn’t really work this way, and CRISPR technology has had fairly limited success so far. But there have been successes, and CRISPR is generally regarded as the Next Great Hope in the future of genetic therapy.

But now there may be a problem. Among the bacteria that use a CRISPER sort of sequence are two that are fairly nasty and common human pathogens. These are Staphylococcus aureus and Streptococcus pyogenes. In fact, the specific CRISPER sequences that genetic scientists use to do the CRISPR thing, come from these specific bacteria.

So, think about this for a moment. If CRISPER is used by bacteria to do any of their dirty work, and the bacteria are common human pathogens, is it possible that some humans have built up an immunity to the CRISPER sequences, perhaps putting them off limits for future CRISPR therapy? Continue reading A Possible Problem with CRISPR

Some good science and thinking related books for you

screen-shot-2017-01-12-at-9-07-03-amA Fortunate Universe: Life in a Finely Tuned Cosmos

This is a concept that has always fascinated me, ever since reading some stuff about the Periodic Table of Elements. Check it out:

Over the last forty years, scientists have uncovered evidence that if the Universe had been forged with even slightly different properties, life as we know it – and life as we can imagine it – would be impossible. Join us on a journey through how we understand the Universe, from its most basic particles and forces, to planets, stars and galaxies, and back through cosmic history to the birth of the cosmos. Conflicting notions about our place in the Universe are defined, defended and critiqued from scientific, philosophical and religious viewpoints. The authors’ engaging and witty style addresses what fine-tuning might mean for the future of physics and the search for the ultimate laws of nature. Tackling difficult questions and providing thought-provoking answers, this volumes challenges us to consider our place in the cosmos, regardless of our initial convictions.

screen-shot-2017-01-12-at-9-12-09-amGetting Risk Right: Understanding the Science of Elusive Health Risks

Understanding risk, and misunderstanding it, became a major topic of discussion, initially in economics, about the time that I was working in a major think tank where much of this discussion was happening. Risk perception had been there as a topic for a while (the head risk-thinker where I worked had already won a Nobel on the topic) but it became a popular topic when a couple of economists figured out how to get the message out to the general public.

In my view, the modern analsyis of risk perception is deeply flawed in certain ways, but very valuable in other ways. This book is very relevant, and very current, and is the go to place to assess health related risk issues, and I think it is very good. I do not agree with everything in it, but smart people reading a smart book … that’s OK, right?

Do cell phones cause brain cancer? Does BPA threaten our health? How safe are certain dietary supplements, especially those containing exotic herbs or small amounts of toxic substances? Is the HPV vaccine safe? We depend on science and medicine as never before, yet there is widespread misinformation and confusion, amplified by the media, regarding what influences our health. In Getting Risk Right, Geoffrey C. Kabat shows how science works?and sometimes doesn’t?and what separates these two very different outcomes.

Kabat seeks to help us distinguish between claims that are supported by solid science and those that are the result of poorly designed or misinterpreted studies. By exploring different examples, he explains why certain risks are worth worrying about, while others are not. He emphasizes the variable quality of research in contested areas of health risks, as well as the professional, political, and methodological factors that can distort the research process. Drawing on recent systematic critiques of biomedical research and on insights from behavioral psychology, Getting Risk Right examines factors both internal and external to the science that can influence what results get attention and how questionable results can be used to support a particular narrative concerning an alleged public health threat. In this book, Kabat provides a much-needed antidote to what has been called “an epidemic of false claims.”

screen-shot-2017-01-12-at-9-19-43-amFeeding the World: Agricultural Research in the Twenty-First Century (Texas A&M AgriLife Research and Extension Service Series)

In the not too distant past, it was understood that we, the humans, were going to run out of food within a certain defined time range. This actually happened several times, this estaimte, followed by the drop-dead date coming and going, and the species continued. Kind of embarassing.

Historically, that estimate of when we would run out of food has been wrong for one, two, or all of three reasons. First, the rate of population increase can be misestimated. We now know a lot more about how that works, and still probably can’t get it right, but in the past, this has been difficult to guess. Second, it hasn’t always been about food production, but rather, distribution or other aspects of the food supply. Right now, the two big factors that need to be addressed in the future are probably commitment to meat and waste. Third, and this is the one factor that people usually think of first, is how much food is produced given the current agricultural technology. That third factor has changed, in the past, several times, usually increasing but sometimes decreasing, depending on the region or crop. Sadly, this is probably also the factor that will change least (in a positive direction) in the future, even given the supposed promise of GMOs, which have so far had almost no effect.

Anyway, this book is about this topic:

The astounding success of agricultural research has enabled farmers to produce increasingly more—and more kinds—of food throughout the world. But with a projected 9 billion people to feed by 2050, veteran researcher Gale Buchanan fears that human confidence in this ample supply, especially in the US, has created unrealistic expectations for the future. Without a working knowledge of what types and amounts of research produced the bounty we enjoy today, we will not be prepared to support the research necessary to face the challenges ahead, including population growth, climate change, and water and energy scarcity.

In this book, Buchanan describes the historical commitment to research and the phenomenal changes it brought to our ability to feed ourselves. He also prescribes a path for the future, pointing the way toward an adequately funded, more creative agricultural research system that involves scientists, administrators, educators, farmers, politicians, and consumers; resides in one “stand alone” agency; enjoys a consistent funding stream; and operates internationally.

screen-shot-2017-01-12-at-9-22-54-amModern Prometheus: Editing the Human Genome with Crispr-Cas9

Gene editing and manipulation has come a long way. We may actually be coming to the point where methods have started to catch up with desire, and applications may start taking up more of the news cycle. We’ll see. Anyway:

Would you change your genes if you could? As we confront the ‘industrial revolution of the genome’, the recent discoveries of Crispr-Cas9 technologies are offering, for the first time, cheap and effective methods for editing the human genome. This opens up startling new opportunities as well as significant ethical uncertainty. Tracing events across a fifty-year period, from the first gene splicing techniques to the present day, this is the story of gene editing – the science, the impact and the potential. Kozubek weaves together the fascinating stories of many of the scientists involved in the development of gene editing technology. Along the way, he demystifies how the technology really works and provides vivid and thought-provoking reflections on the continuing ethical debate. Ultimately, Kozubek places the debate in its historical and scientific context to consider both what drives scientific discovery and the implications of the ‘commodification’ of life.

Genetics and Food Security

There is a food crisis sneaking up on us right now. A lot of them, actually. A lot of little one, some big ones. There are always places in the world where food has become scarce for at time, and people starve or move. You’ve heard of the “”Syrian refugee crisis,” and the often extreme reactions to it in Europe and among some in the US. That started out as a food crisis, brought on by human pollution induced global warming in an already arid agricultural zone.

Nearly similar levels of climate change related pressure on agricultural systems elsewhere has led to very different outcomes, sometimes more adaptive outcomes that won’t (at least for now) lead to major geopolitical catastrophes as we have now in the Levant and elsewhere in West Asia. What’s the difference? The difference is how agriculture is done.

Are GMOs a solution? Are GMOs safe, and can the produce a small or medium size revolution in crop productivity? What about upgrading traditional agriculture to “industrial agriculture”?

And speaking of GMOs, what is the latest in GMO research? How should GMOs be regulated, by the method they are produced, or by the novel or altered traits they have? How do we communicate about GMO research and GMO crops? What about labeling?

These and many other questions are addressed ad Mike Haubrich, me, and Anastasia Bodnar talk about “Genetics and Food Security” on the latest installment of the Ikonokast Podcast. GO HERE to listen to the podcast. Also, if you go there, you can see a picture of Anastasia holding her latest GMO product, a corn plant that can see and talk!

Also, Iknokast has a Facebook Group. Please click here to go and joint it!

And, if you have not yet listened to our first podcast, with author and science advocate Shawn Otto, click here to catch up!

Temperature and sex determination

Some interesting new research. The paper is, unfortunately, behind a paywall but they made a video, so it is worth posting.

Here’s the press release for the paper:

Scientists know that temperature determines sex in certain reptiles—alligators, lizards, turtles, and possibly dinosaurs. In many turtles, warm temperatures during incubation create females. Cold temperatures, males. But no one understands why.

A recent study sheds further light on this question. The findings of researchers Kayla Bieser, assistant professor at Northland College, and Thane Wibbels, professor of reproductive biology at the University of Alabama at Birmingham, will be published this month in the primary research journal “Sexual Development,” and is now available online.

This study represents the most comprehensive, simultaneous evaluation of the chronology of how sex-determining genes express themselves during embryonic development and and looks at the impacts of estrogen.

Bieser and Wibbels followed five different genes and what was going on in the exact same turtle. To date, scientists have looked at a number of turtles and pooled the data but Bieser is the first to follow individual turtles. She wanted to know when and how they “express” themselves. For an example, Bieser describes expression as the physical manifestation of those genes such as blue or brown eye color.

She looked at turtle eggs incubated at male and female temperatures and documented what the genes were doing while sex is being determined. “Which genes ‘turn on’ and when, could be an indication of what is triggering sex,” Bieser said.

According to Bieser, temperature-dependent sex determination species may be unable to evolve rapidly enough to offset the increases in temperature, which may ultimately result in their extinction.

“It’s critical that we understand the genetic mechanisms for which temperature acts and incorporate this knowledge into management plans for the conservation of these vulnerable species.”

Secondly, Bieser applied estrogen to eggs at a male-producing temperature. The purpose she said is to help determine the triggers for sex determination and how hormones, such as estrogen, can override the temperature signal.

In other words, would temperature or estrogen win out in deciding sex? The answer: in short, neither. What she found — and this is new information — is when estrogen is applied to eggs incubating at a male temperature, gonads—or sexual parts—do not develop. Or, if they do, they barely develop.

Why? “We don’t know yet,” Bieser said.

Scientists have been doing this experiment for some time but never reported these results. She suspects the reason is because scientists did not dissect the gonadal area specifically and that they took the general area but may have not analyzed the gonads to the same detailed level. In fact, this was a sticking point for one of the reviewers of this study—so Bieser provided photos of her findings.

“This research provides a critical understanding of how temperature acts on and above the genes in species where temperature determines sex—this is particularly critical in light of global climate change,” Bieser said.

Here’s the video:

The original paper:
Bieser K.L. · Wibbels T. 2014. Chronology, Magnitude and Duration of Expression of Putative Sex-Determining/Differentiation Genes in a Turtle with Temperature-Dependent Sex Determination. Sexual Development 8(6).

It turns out that coffee is special

But you knew that already.

The Coffea canephora Genome has been sequenced. This is probably more important than the Human Genome project because humans are completely useless first thing in the morning, but coffee is very important first thing in the morning.

Some important plant evolution involves wholesale duplication of large parts of the genome. This does not appear to be the case with coffee. Rather, diversification of single genes characterizes the genome, so, according to the paper reporting these results in Science, “…the genome includes several species-specific gene family expansions, among them N-methyltransferases (NMTs) involved in caffeine production, defense-related genes, and alkaloid and flavonoid enzymes involved in secondary compound synthesis.”

Also of great interest is the apparent fact that caffeine related genes either evolved separately from, or engaged in the important work of making caffeine separately from similarly functioning sets of genes in tea and cacao (chocolate). I had always suspected tea was … different.

So, not at all unexpectedly, the most important molecule on earth evolved more than once!

Elizabeth Pennisi also has a writeup here.

How to do any genetic research you want without getting permission.

Let’s say you want to do a market-related study in which you gain entry to one thousand homes representing sets of people defined by the usual variables of income, ethnicity, urban-suburban lifestyle etc. The first thing you do is to ask a few people, real nice like, if you can go through their stuff and take a lot of photographs and notes. Most of them say no, and you perhaps even discover that the one or two who actually agree to this are odd ducks. So you go to Plan B. This involves breaking into the homes when the people are out so you can get your data despite the fact that they don’t want to participate. But you get caught and can’t do that any more. So, now you are faced with the reality that your research plans are done for.

But wait, there is a way to get similar data without needing any permission from anyone and it is not illegal, and in fact, it could actually be cheaper and easier than your original proposal and, while it may not provide the same exact results, it could even provide BETTER results. Let’s call it Plan C.

Plan C involves looking at every iteration of every single Google Street View picture ever taken anywhere in the US at any time. All of them. The vast majority of these photographs will show you nothing, but every here and there, you will get some data. There will be a shot that shows a thing in an open window, or an open door, or an open garage, or being carried into our out of a person’s house, being delivered, thrown out on the curb, sold in a garage sale, sitting on the lawn after an explosion or fire, or in use (especially yard and garden implements). This is not the same thing as sampling hundreds of houses once each, looking at all contents. But it is sampling the homes lived in by hundreds of millions of people, and sampling them dozens of times over a few years. That could be some amazing data.

And nobody can stop you from studying this source of information or doing this research. If someone does try to stop you with silly regulations from a University or something, just change into a Journalist. Then you’re golden. It would be WRONG to stop a journalist from using this information!

Turns out that this works with genes, but even better. One might want to study the relationship between a putative genetic marker and a possible behavioral thing, like maybe a psychiatric disorder or something, in a genetically bottle necked tribal group somewhere. You can try to get permission to do this, and maybe you’ll get it. Maybe you won’t get permission but you can certainly steal the genetic data from some place and do the research anyway. But people will get mad at you and you’ll not get any more research money.

Or, you can go to Plan C.

Here’s how Plan C works with genes. We have a good idea of the distribution of many genetic markers that have to do with geographical patterns over time. (Some people would use the term “race” in that sentence but that’s incorrect and unnecessary.) So, something like “East Asian” or “Native South American” or “Central African” or whatever has a list of genetic markers that go with it. Genes are supposed to “independently assort” and act all random and all, but they don’t. At the finest level, on chromosomes, genetic markers that are near each other travel together because of “linkage.” More importantly, genes move in populations. So, those East Asian genetic markers are not going to get all mixed up with the Central African genetic markers too often. Also, if you have enough samples, some mixing up doesn’t matter all that much.

So, if you want to study a disease-related “gene” (allele, a variant of a gene, really), if you think such a thing exists, you can effectively study it in a small population of repressed brown people who, tired of repression and exploitation decided to be totally unfair to you and not give you their blood, by looking at the association of LBP (“little brown people”) markers and the alleles of interest. It does not even matter if many of those marker associations are found in totally non LBP people. They are still associated. Genetic lineages are the thing, not human lineages. Humans are merely reasonable approximations of genes, really. Or at least, you can make a case for the associations and get your research funded and published without asking anybody any permissions for anything, just using giant available genetic databases. OK, so, maybe this is not “any genetic research you want.” But it is without permission!

This all sounds very nefarious but may not be. Or maybe it is. I’ll leave that to the ethicists.

By the way, if you are interesting in a big fight on the Internet about genetic research, ethics, “IRB” permissions, LBP’s and science and so on and so forth, I recommend the following, in the order suggested.

First, read this blog post: Is the Havasupai Indian Case a Fairy Tale? by Ricki Lewis (and if you have time, along with it, this related blog post)


Then, read this blog post: The Empire Strikes Back by Jonathan Marks

Then, go back to the first blog post (Is the Havasupai Indian Case a Fairy Tale?) and read the comments.

Then, report back here and tell me what you think. Especially about that last comment on the PLOS blog post.

Have a nice evening!

Photo Credit: tapasparida via Compfight cc

Regenesis: Taking over biology using readily available materials from your kitchen

I might be exaggerating slightly about the ready availability of the materials…

Regenesis: How Synthetic Biology Will Reinvent Nature and Ourselves by George Church and Ed Regis looks like a futurist tome on what could happen when technology finally catches up with human imagination and everything changes. Except it isn’t. Most futurists are people with some knowledge of technology, a fertile imagination, and a publicist. Regenesis is by a scientist (working with a writer) who is busy making a different future and who has been involved in every stage of development of the technology under discussion, and for this reason is one of the more important new science-related books you can read right now. Regis is a multiply published science author (his most recent book is What Is Life?: Investigating the Nature of Life in the Age of Synthetic Biology) and George Church is Professor of Genetics at Harvard Medical School who is one of the key players in the Personal Genome Project. He directs Personal Genomics.org, which curates the only OpenAccess human “Genomic, Environmental and Trait database. His work led to the first commercial genome sequence (for apathogen) and he has been involved in both genome sequencing (reading the genes) and synthesis (making new ones) in both the academic and private milieu. He is also director of the NIH “Center for Excellence in Genomic Science” which places him at the center of biosafety, gene privacy, and security policy development.

Church was finishing is PhD work at Harvard the same year that I started mine. We never met to my knowledge, but I remember the construction in those days of the new genetic research facility there. Cambridge, Massachusetts was the first and only city (and still maybe the only one) to write zoning and building regulations for genetic research facilities, and the building was right across from the museum I worked in. People were afraid of what might happen if some of the genes, or genetically modified organisms, they were working on in that building got out. That was a valid concern given the unknowns, but it would eventually happen that the details of what people needed to worry about shifted considerably over time. Had George Church been sent back in a time capsule and put in charge of that project, his understanding of and commitment to safety in genetic research would have been more than a little reassuring. Of course, this would have then affected his own future and thus … oh never mind, that damn Time Paradox is too confusing…

Regenesis covers the history and current status of some of the most innovative and interesting research in genetic engineering, and it is organized in a way that I really liked. The book is written as a time line. The chapters run as follows:

  • -3,800 Myr, Late Hadan
  • -3,500 Myr, Archean
  • -500 Myr, Cambrian
  • -360 Myr, Carboniferous
  • -60 Myr, Paleocene
  • -30,000 YR, Pleistocene Park
  • -10,000 YR, Neolithic
  • -100 Yr, Anthropocene
  • -1 Yr, Holocene
  • +1 Yr, The End of the Beginning, Transhumanis, and the Panspermia Era

See what they did there?

Each of these past eras represents a change in the genetics, cellular biology, evolutionary stage, or environmental context in which live existed, with the human role coming along in a big way near the end. This allows the authors to discuss the nature of life at each stage, and related the last 20 or so years of genomic and genetic research to different levels of organization of life. This causes this book to be different from the average run of the mill futurist book in two ways: 1) You learn stuff about how things are and have been, detailed stuff, interesting stuff; and 2) There is a solid road map imposed on the discussion of what is being done now and what could be done in the future, which allows the authors to avoid the messing around we see in a lot of futurist books. In other words, this is not futurist manifest; It is a history of life and a detailed discussion of what humans are actually doing with life these days and what we seem poised to be able to do based on a solid grounding in actual ongoing research.

One of the most interesting themes that helps underscore the nature of this discussion is left- vs right-handedness in biology. Most complex biological molecules could be built with the structure and symmetry organized in a left handed vs right handed way. It is quite possible that we could encounter a planet (if we could get there) rich in life that is all built on molecules that are the opposite in orientation from what we have here on Earth. Not only that, but it is possible to build such a life form now. We could construct a human that is left-handed, and thus, fundamentally different from all other humans. Such a human could not be infected by many, perhaps most, cell-level pathogens because those pathogens would not be able to interact with the left-handed body. Obviously, this is a complex issue and there is a lot too it…you’ll have to read the book to find out what the implications and complications of such a thing might be.

The most important theme in the book, and also very interesting, is the concept of synthetic biology. The goal of synthetic biology is to create an organism or set of organisms that use the standard biological machinery (proteins and enzymes and stuff building other molecules in a certain way) that will be instructed with their DNA to produce a certain product, such as oil, a house, a cute little furry organism that will replace your Roomba. Well, maybe not that last one. We use lots of synthetic biology now but we are at the chipped-stone tool phase. The basics are in place, the research is progressing, the market for the products is there. Synthetic biology is one of those “technologies” that many hope will come along and solve many of our problems. It should be relatively straight forward to create a thing that will make hydrocarbon based fuels, which one must admit are a very handy way of storing energy, from raw materials that do not include fossil carbon. My personal fantasy is to build large flat factories on the sea surface or in open arid regions that will produce a solid that we just pile up somewhere to contain carbon taken from the atmosphere, and a steady stream of a clean burning liquid. Down the street, I want to see a factory that consist of a giant, 30 acre leaf surface under which is constantly being built a layer of genetically engineered wood, with whatever properties are needed. Imagine 2X4s of just the right strength and flexibility, but indurated with anti-fungicidal and other preservative chemicals. A combination of balsa, ebony, maple, cedar and hickory. Left-handed, of course. Who needs plastic and concrete when we have Frankewood! Bwahahaha!

I interviewed George Church a couple of weeks ago on the radio. The podcast of that interview is located hare on iTunes
icon, or you can find out other ways to get it or listen to it directly here.

From the official description of the book:

Imagine a future in which human beings have become immune to all viruses, in which bacteria can custom-produce everyday items, like a drinking cup, or generate enough electricity to end oil dependency. Building a house would entail no more work than planting a seed in the ground. These scenarios may seem far-fetched, but pioneering geneticist George Church and science writer Ed Regis show that synthetic biology is bringing us ever closer to making such visions a reality.

In Regenesis, Church and Regis explorethe possibilities—and perils—of the emerging field of synthetic biology. Synthetic biology, in which living organisms are selectively altered by modifying substantial portions of their genomes, allows for the creation of entirely new species of organisms. Until now, nature has been the exclusive arbiter of life, death, and evolution; with synthetic biology, we now have the potential to write our own biological future. Indeed, as Church and Regis show, it even enables us to revisit crucial points in the evolution of life and, through synthetic biological techniques, choose different paths from those nature originally took.

The Genetics of Pesticide Resistant Bedbugs

ResearchBlogging.orgBedbugs (Insects of the Cimicidae family, commonly Cimex lectularius) are annoying, might carry diseases (though this is unclear, so probably nothing importat1, and are apparently becoming more common in the US. Interestingly, there has been very little study done of their genetics. A new study just out in PLoS ONE looks at the bedbug genome in an effort to better understand pesticide resistance in these pesky critters.

Continue reading The Genetics of Pesticide Resistant Bedbugs

What is the most important human adaptation?

Human infants require more care than they should, if we form our expectations based on closely related species (apes, and more generally, Old World simian primates). It has been said that humans are born three months early. This is not accurate. It was thought that our body size predicted a 12 month gestation, and some suggested that Neanderthals would have had such, but this research conclusion has been set aside based on new analysis. But it is still true that developmentally, human children do not reach a stage of development that allows some degree of self care for a very long time compared to apes. The actual sequence of development is not directly comparable: It is not the case that after a certain amount of time humans reach a specific stage reached earlier in the lifecycle by Chimpanzees, as the differences are more complicated than that. For the present purposes, we can characterize the human condition for early development like this: Human babies are more helpless in more ways and for longer than comparable ape babies.
Continue reading What is the most important human adaptation?

Evolutionary enamel loss linked to molecular decay of enamel-specific gene

The evolutionary history of mammals can be reviewed as the evolutionary history of tooth loss. The early mammals had many teeth, and every now and then in evolutionary time, a tooth is lost wiht subsequent species arriving from that n-1 toothed form having that smaller number of teeth. With ver few exceptions, no mammals have added a tooth during the history of mammals. (Excepting maybe the very very earliest period, but probably not.)

ResearchBlogging.orgWell, the loss of enamel itself is also an evolutionary trend in mammal history, and recent research published in PLoS Genetic associates genetic changes over time with what is known of the morphological evolution of mammals.

Continue reading Evolutionary enamel loss linked to molecular decay of enamel-specific gene