22 votes

Why do we have more male infants born?

Note: This is based on literature searches I've done a while ago out of general curiosity. I'm in no way an expert on human reproduction. First, I'm not sure if you are asking about evolutionary ...
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16 votes

Are there examples of animals being sexually attracted to another species more than to their own?

Here are a few examples. All are open to debate as to whether it answers your question. Zoophilia in humans When asking of example of a "species" that does something, it is easy to forget about the ...
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  • 67.5k
12 votes
Accepted

Why does sex last so long?

There are plenty of animals with brief procreative periods, as you suggest. In chimps, sex takes 10 to 15 seconds - much less time than humans. So the question is really why have humans evolved to be ...
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  • 6,771
9 votes

Why are men stronger than women?

What are the evolutionary explanations for why women are weaker than men (on average), and is this difference adaptive? All of the theories surrounding this fact are speculative; it would be ...
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  • 9,054
9 votes

Why do we have more male infants born?

There is an article in the Journal of Popular Science from 1885. However, I do know there is at least one more recent article floating around some where since I read it. At the moment, I can't find it ...
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  • 2,167
8 votes

Why does sex last so long?

I'm going to give a tentative answer full of speculation and guesswork, but it's too long to fit in a comment so here goes. Sex duration is possibly a sort of human reproductive handicap. Sexual ...
7 votes

Does any animal species have two sexes and more genders?

Many organisms have multiple sexes. For instance, here is one which apparently has 7 (and each sex, or "mating type" can only mate with the others). The "gotcha" is that, mostly, they're unicellular ...
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  • 4,460
7 votes

Is sexual selection evolutionarily advantageous?

What does "evolutionary advantageous" mean? First note that is sexual selection evolutionarily advantageous? is a question that makes no sense. An allele or a ...
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  • 67.5k
7 votes
Accepted

Are there examples of selection on males influencing female phenotypes?

Selection in one sex can produce a correlated response in the other when there is pleiotropy (or linkage disequilibrium) (see Lynch & Walsh 1998, and Lande 1979 & 1980). Genes can be ...
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  • 16k
7 votes
Accepted

Is a female spider, well-fed by sexual cannibalism, less likely to mate again?

It does appear that Wikipedia has not provided the most appropriate reference for that statement, but it is repeated in the article it refers to and that you link to, both in the abstract: Male ...
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  • 34.9k
7 votes
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Isn't sexy son hypothesis circular?

The process is self-reinforcing but the argument is not circular (no tautology implied). As soon as some male traits are considered more sexy than others, then there is selection for females to like ...
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  • 67.5k
5 votes

Are we more attracted to people of the same ethnicity?

The answer in extreme brief is yes. Only about 9% of whites and 16% of blacks engage in interracial marriage in the U.S. But really this deserves a fuller discussion. The predominant pattern of ...
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  • 27.4k
5 votes

How can homosexuality evolve despite natural selection?

There is an interesting theory coming from a slightly different, yet related, field. It was developed by Paul Vasey and Doug VanderLaan of the University of Lethbridge, they are both evolutionary ...
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  • 491
4 votes

Why are not all species hermaphrodites?

I'm not at a biologist, but I have a pet theory I'd like to throw into the ring: hermaphroditism tends to be unstable in a similar way to strong sex skews. Imagine species A where 90% of offspring ...
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4 votes

Does any animal species have two sexes and more genders?

Yes, it is called Alternative Mating Strategies and is well known. As an example High-backed pygmy swordtail (a fish) are known for having two types of males, one that is large and aggressive and ...
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  • 13.1k
4 votes
Accepted

Why estimate linear and full (linear, quadratic, and correlational) selection coefficients separately?

This is directly following the advice of Lande & Arnold (1983), saying: Linear multiple regression can be used first to estimate the forces of directional selection, $\beta$, and their ...
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4 votes

Is the golden ratio of anatomic measurements universally beneficial for sexual reproduction?

I have some insight into this from an engineering perspective. Years ago, I worked on some computational and search algorithms which used a growth factor to determine how far to widen a search space, ...
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4 votes

Role of drift in evolution of sexually dimorphic traits

[C]an drift overcome sexual selection in the evolution of sexually dimorphic traits? Short answer Yes Long answer There are many ways to consider the effect of genetic drift. Here is one: One can ...
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  • 67.5k
4 votes

How is "selection" best defined?

My favourite definition Selection is a fitness differential associated to a genetic variance among individuals in a population. You might want to have a look at What does fitness really mean?. What ...
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  • 67.5k
4 votes

Does sperm weight causes sex ratio?

Probably not! There are certainly some physical reasons to doubt it. Looks like the mass difference between X and Y sperm is on the order of 0.1 picograms: X chromosome "weight"? First, ...
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  • 279
4 votes

Isn't sexy son hypothesis circular?

Taken by itself I can agree that it might seem circular. However, in practice, all traits act and occur in a pre-existing background, i.e. in organisms with their genetic background and their living ...
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4 votes

Why are (some) male humans sexually attracted to the breasts of female humans?

Short answer, we don't know. There are several competing hypotheses but they are all nearly impossible to test. Behavior often suffers the same problem as testing, we can come up with a hypothetical ...
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  • 13.1k
4 votes
Accepted

How does natural selection explain sexual display?

Short answer Survival does not get your genes into the gene pool, reproduction does. thus reproduction based selective pressures can be stronger than survival based ones. there are plenty of organisms ...
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  • 13.1k
3 votes
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Selection Pressure on Orca Whale Coloration

You can find a discussion of this topic in the literature: Mitchell, Edward. 1970. Pigmentation pattern evolution in delphinid cetaceans: an essay in adaptive coloration. Canadian journal of Zoology ...
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3 votes

Does any animal species have two sexes and more genders?

The closest thing you will find to what you're looking for, I think, are animals with multiple different mating strategies where one sex (usually the male) can have multiple distinct phenotypes. Some ...
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  • 2,373
3 votes

Does any animal species have two sexes and more genders?

There are hermaphrodites and gender changing (M->F, F->M) fish. Also occasionally, there are also individuals who are neither male nor female, which may or may not count here. However, I haven't ...
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  • 27.4k
3 votes

Does any animal species have two sexes and more genders?

I'm not sure what you mean by "gender" in the context of non-human organisms. Gender is usually defined as the intersection between biologically determined sex, and the surrounding culture. Maybe ...
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  • 4,680
3 votes

Do men have more extreme variations than women?

So far as we can tell any difference in variability (standard deviation) in humans is cultural not genetic and thus not consistent across the species. You are talking about something called the ...
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  • 13.1k
3 votes
Accepted

Is mate choice in non-human primates MHC-dependent?

tl;dr It's messy for non-human primates too. Winternitz et al. (2017) ("Patterns of MHC‐dependent mate selection in humans and nonhuman primates: a meta‐analysis", Molecular Ecology 26(2)) review ...
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