Tag Archives: Sex Differences

Topi or not Topi …

i-e1003b13638050040bea14fa3d3fabe0-repost.jpgGo to any bar and you’ll see a lot of males standing and sitting around not mating. I’ll bet you would have guessed that the reason they are not mating is that no females will mate with them for one reason or another. But there is the distinct possibility that they are very inconspicuously resisting mating opportunities. It turns out that males can do this …. avoid mating without conspicuous resistance … more easily than females. For obvious reasons.

This could be why what has become (inappropriately) known as “reversed sexual aggression” often goes unnoticed, and a recent study of the African antelope Damaliscus lunatus (a.k.a. “topi”) explores this possibility.

Continue reading Topi or not Topi …

Chimpanzee Food Sharing

Is chimpanzee food sharing an example of food for sex?

i-3691706735948748b5a89f0a306951ac-chimp_share_tree.jpg
One of the most important transitions in human evolution may have been the incorporation of regular food sharing into the day to day ecology of our species or our ancestors. Although this has been recognized as potentially significant for some time, it was probably the Africanist archaeologist Glynn Isaac who impressed on the academic community the importance of the origins of food sharing as a key evolutionary moment. At that time, food sharing among apes was thought to be very rare, outside of mother-infant dyads. Further research has shown that it is in fact rare … the vast majority of calories consumed by human foragers in certain societies and at certain times of the year comes from a sharing system, while the fast majority of calories consumed by chimpanzees is hand to mouth without sharing.
Continue reading Chimpanzee Food Sharing

Marta’s (good) questions, … fur

Why did humans evolve hairlessness? Hair (fur) protects mammals from heat and cold, what would be the benefit from losing this asset?

I think the most commonly held theory is that fur works on quadrupeds, but once you stand upright, it is less effective, and less fur works better. For later time periods, clothing works better than fur because it is more adaptable. Consider that whatever fur-based system human ancestors had was based on needs in the tropics where it does not get that cold, so it is not hard to imagine that clothing is much more effective.

Recent studies of body parasites suggest that body lice unique to humans differentiated genetically only fairly recently, in the range of several tens of thousands of years. This body lice requires clothing … human clothing on human bodies is the habitat for these lice. This suggests there may have been a reduction from a certain level of furriness only with modern humans living in a wide range of environments and using controlled fire, clothing, and some kind of shelter (hut/house) to deal with the elements. So it is possible that the immediate ancestors to modern humans (perhaps Homo erectus?) were actually fairly furry.

As for details of the body hair, this is also interesting. Why do humans have pubic hair but not a lot of other hair? Why to males have more body hair than females in many cases? Why to human males have facial hair? The African Apes have much less facial hair than most modern human males. It has been suggested that this has to do with sexual selection. It is important to distinguish between the idea that the starting condition is a lot of fur and that females may have lost more than males, vs. the starting condition was very little hair and males have added more. The amount of fur, it’s appearance, etc. may be related to testosterone (this is true in males and females but more obvious in males) so facial hair may be a signal of “quality” in males.

I’m a little worried

The following is a proof developed by a number of economists at Harvard. It is a proof of the inability of women to understand technologically complex problems, math, engineering, that sort of thing. it is claimed that it almost always works.

Now, I’m not saying that Larry Summers was party to this proof, or even in the room at the time. I’m. Not. Saying. That.
Continue reading I’m a little worried

Sex Ratio Bias in India

Sometimes boys are worth more, sometimes girls are worth more. In an evolutionary sense. Or, more correctly, the value of a certain sex … as an offspring … can be measured in fitness terms. Fisher noted this and hypothesized this was the explanation for the 50-50 sex ratio we usually see. As one sex becomes more rare, it becomes more valuable, and thus parents (mothers, perhaps, usually) bias towards that sex. Then the disparity goes away and thus the differential value goes away.Of course, the truth is that we don’t actually see the 50-50 sex ratio all the time … many species of organisms have a highly biased sex ratio. Many have a highly biased ratio in adults, much more biased than in offspring. This sort of thing varies quite a bit. But what about humans, and what about the report that Indian girl-boy ratios at ‘all-time low’ … Continue reading Sex Ratio Bias in India

Female Coders Do It With Consideration

Check it out:

Emma McGrattan, the senior vice-president of engineering for computer-database company Ingres-and one of Silicon Valley’s highest-ranking female programmers-insists that men and women write code differently. Women are more touchy-feely and considerate of those who will use the code later, she says. They’ll intersperse their code-those strings of instructions that result in nifty applications and programs-with helpful comments and directions, explaining why they wrote the lines the way they did and exactly how they did it.The code becomes a type of “roadmap” for others who might want to alter it or add to it later, says McGrattan, a native of Ireland who has been with Ingres since 1992.Men, on the other hand, have no such pretenses.

Continue reading Female Coders Do It With Consideration

The Phalarope: Not just another polyandrous bird…

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MIT researchers found that phalaropes depend on a surface interaction known as contact angle hysteresis to propel drops of water containing prey upward to their throats. Photo by Robert Lewis
The Phalarope starts out as an interesting bird because of its “reversed” sex-role mating behavior. For at least some species of Phalarope, females dominate males, forcing them to build nests and to care for the eggs that the females place there after mating. If a female suspects that a male is caring for eggs of another female, she may destroy the eggs and force the male to copulate with her a few times, after which she places the newly fertilized eggs in his nest. This polyandrous behavior is probably facilitated by the fact that the lady phalaropes, denizens of extreme climates with short breeding seasons, are capable of rapid egg production … so their egg production converges, kinda, on sperm production … thus allowing them to exploit multiple males for their parenting behavior.Well, it turns out that these birds are interesting in another way: They defy gravity! … sort of … read on:

As Charles Darwin showed nearly 150 years ago, bird beaks are exquisitely adapted to the birds’ feeding strategy. A team of MIT mathematicians and engineers has now explained exactly how some shorebirds use their long, thin beaks to defy gravity and transport food into their mouths.The phalarope, commonly found in western North America, takes advantage of surface interactions between its beak and water droplets to propel bits of food from the tip of its long beak to its mouth, the research team reports in the May 16 issue of Science.These surface interactions depend on the chemical properties of the liquid involved, so phalaropes and about 20 other birds species that use this mechanism are extremely sensitive to anything that contaminates the water surface, especially detergents or oil.

Continue reading The Phalarope: Not just another polyandrous bird…

Proof that Noah’s Ark was Real

One of the most compelling argument that the story of Noah’s Ark is made up is the implausibility of having animals like tigers and lions together with animals like lambs and deer on the same boat for very long. The big carnivores would eventually eat the little cute furry things. The bunnies would be the first to go. But new evidence, shown on the Miracle Pet Show disproves this objection. Continue reading Proof that Noah’s Ark was Real

The Modes of Natural Selection

There many ways of dividing up and categorizing Natural Selection. For example, there are the Natural Selection, Sexual Selection and Artificial Selection, and then there is the Modes of Selection (Stabilizing, Directional, and Disruptive) trichotomy.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. Continue reading The Modes of Natural Selection

The Buttocks is not an excretory organ

… but it might be a sexual organ…

The Federal Communications Commission has proposed a $1.4 million fine against 52 ABC Television Network stations over a 2003 broadcast of cop drama NYPD Blue….The fine is for a scene where a boy surprises a woman as she prepares to take a shower. The scene depicted “multiple, close-up views” of the woman’s “nude buttocks” according to an agency order issued late Friday….The agency said the show was indecent because “it depicts sexual organs and excretory organs , specifically an adult woman’s buttocks.”The agency rejected the network’s argument that “the buttocks are not a sexual organ.”[source]

Continue reading The Buttocks is not an excretory organ

Chimpanzee Food Sharing

Is chimpanzee food sharing an example of food for sex?

i-3691706735948748b5a89f0a306951ac-chimp_share_tree.jpgOne of the most important transitions in human evolution may have been the incorporation of regular food sharing into the day to day ecology of our species or our ancestors. Although this has been recognized as potentially significant for some time, it was probably the Africanist archaeologist Glynn Isaac who impressed on the academic community the importance of the origins of food sharing as a key evolutionary moment. At that time, food sharing among apes was thought to be very rare, outside of mother-infant dyads. Further research has shown that it is in fact rare … the vast majority of calories consumed by human foragers in certain societies and at certain times of the year comes from a sharing system, while the fast majority of calories consumed by chimpanzees is hand to mouth without sharing.

Continue reading Chimpanzee Food Sharing

Why is There no Birth Control Pill for Men?

i-fc0baa42c324cefa8495fdb0044234b2-dice.jpg Why is there no Birth Control Pill for men?This latest “Ask a ScienceBlogger” question will certainly engender a wide range of responses from the Scienceblogs.com team. Answers may address physiology, endocrinology, pharmacology, economics, and other areas of scientific thinking and practice. The answer I’d like to propose can be summed up in two closely linked words pilfered from the question itself: Continue reading Why is There no Birth Control Pill for Men?