Comments on: Why do we still vary?

By: Tomasz R.

Tomasz R. — Tue, 25 Oct 2011 19:56:11 +0000

Height is not necessairly good. Taller heigh means a lot of growth hormone which increases chances for getting cancer. Most long-lived people are not tall.

By: Justin Giancola

Justin Giancola — Sun, 23 Oct 2011 06:05:47 +0000

http://dienekes.blogspot.com/2011/10/short-legged-neandertal-mystery-solved.html

No way … I theorized along these lines years ago! awesome.

I wonder if they’ll look into the musculature of the calf as well – as well as attributes of pelvic and foot bones.

By: silylene

silylene — Sun, 23 Oct 2011 02:13:31 +0000

Sometimes increasing height is not always a positive selection. I can think of two examples:
- In WW1, shorter infantry men had a higher survivability than taller men, with a strong correlation. I read a nice paper on this about 25 yrs ago. The authors speculated that being tall increased one’s risk of dying in trench warfare.
- Height also corresponds better to leg length than trunk length (there is more variation in leg length than trunk length). Dienekes just wrote a short article on why shorter legs are advantageous to populations who live in mountainous regions. http://dienekes.blogspot.com/2011/10/short-legged-neandertal-mystery-solved.html This fits well with some of my observations also of shorter legged people living in Bolivia and Peru, or even in Greece compared to leggy people from the the flatlands such as Netherlands or the African plains.

By: Mark Houston

Mark Houston — Sat, 22 Oct 2011 06:49:31 +0000

Maybe the question everyone should be asking is – WHY ARE THERE TALL PEOPLE. After all, Christopher Ruff and Tom Samaras would both laugh at the thought that being small is odd.

By: Nick Rowe

Nick Rowe — Sat, 22 Oct 2011 01:49:45 +0000

Empirical evidence here that tall men are more likely to be married, even adjusting for age and income etc. :

http://worthwhile.typepad.com/worthwhile_canadian_initi/2011/10/in-applied-economic-research-what-actually-matters.html

By: rob

rob — Fri, 21 Oct 2011 05:15:59 +0000

Maybe within population variation height works like schizotypy (or whatever we call that now) and intelligence maybe work. There can be lots of variation despite directional selection because genes break faster that selection can remove them. Kinda makes sense, tons of genes influence the trait, no common alleles have a huge effect. Probably the general rule for quantitative traits.

By: twl

twl — Thu, 20 Oct 2011 23:07:43 +0000

//When I asked the women the same question, roughly two-thirds (out of 150) said they choose based on height.//

Who amongst you is NOT forced to date sub-standard mates because you can’t attract a tall guy? Put up your hands now!

By: Charles Nydorf

Charles Nydorf — Thu, 20 Oct 2011 12:23:45 +0000

Thank you, John Hawks and Rich Lawler!

By: Steve Sailer

Steve Sailer — Thu, 20 Oct 2011 12:12:33 +0000

I’m a little over 6’4″, and I find being tall pretty useless other than for seeing over other spectators at golf tournaments. It used to be a good clue to how well fed you were as a child, but fortunately that’s becoming less meaningful. Personally, I think tall genes exist to fool other people into thinking you are from a wealthy family. We’re used to people using nurture to try to fool other people about their nature, but I think this is the mirror image. The main advantage to being tall was that other people assumed you must come from a well-to-do family.

By: Razib Khan

Razib Khan — Thu, 20 Oct 2011 03:11:22 +0000

#28, me like. no apology needed!

By: rich lawler

rich lawler — Thu, 20 Oct 2011 02:58:07 +0000

One overlooked concept is that sexual selection can actually act to increase genetic variability. So if height is a sexually-selected trait due to female choice, this can lead to increased genetic variation due to selection for modifier loci that have beneficial mutations that hitchhike on loci contributing to the selected trait. I think there are a few models out there (by Pomiankowski and by Petrie) that show how female choice creates genetic variability in the selected trait. Basically, models that incorporate biased-mutation versus those that don’t can change the direction of the variance we expect to see in traits under selection (Hanna Kokko reviews this in her 2006 paper on ‘unifying models of sexual selection’).

Also, a minor point: directional selection (acting on the mean) can occur independently–and often does occur independently–of selection acting on the variance, since the moderate amounts of phenotypic variation observed in traits under directional selection out in nature (not in fruit flies or corn) is proof-positive that it must.

In response to John Hawk’s comment, I think Gunter Wagner has already modeled this in terms of morphological evolution in his paper on “the influence of variation and developmental constraints on the rate of multivariate evolution…” (in J. Evol Biol 1988). This is known as the ‘corridor model” where variation is allocated in one direction but constrained in another, thus limiting what variation gets expressed when traits are linked. Something like that.

wow, this was one pedantic post…sorry.

By: John Hawks

John Hawks — Thu, 20 Oct 2011 02:27:18 +0000

“Genes which have small effect in height may have larger effect in other traits which are constrained from shifting in allele frequency too much.” This sounds perfectly reasonable. Will someone please accept Razib’s challenge and formulate this in a quantitative model?”

For a few-locus system, it could be reasonable for directional selection on stature to be balanced by selection on the pleiotropic effects of the genes that explain the additive variance in stature. Directional selection means that stature and fitness covary; if pleiotropic traits also covary with fitness, the net additive variance in fitness could be zero even with substantial additive variance in stature.

For stature, the additive variance is spread across too many loci for this model to be plausible. We presently know of more than 300 loci that contribute to the additive variance, and together they account for only a fraction of the additive variance. There must be many, many more, maybe even so many that new or recent mutations comprise an appreciable fraction of the additive variance. There should be plenty of additive variance that can respond to directional selection on height.

By: Eurologist

Eurologist — Thu, 20 Oct 2011 02:03:22 +0000

“I saw somewhere that while men everywhere largely agree on who is and isn’t an attractive woman, who women find attractive has no apparent general agreement and varies widely.

It’s as if women are designed specifically to have various interests in mate selection as a way of maintaining genetic variety, and height is a part of this.”

Not only that, but women’s attraction towards men changes during the menstrual cycle, with attraction towards more masculine and athletic types around ovulation, and more “caretaker” types at other times.

By: Brian Schmidt

Brian Schmidt — Thu, 20 Oct 2011 00:50:01 +0000

While height may be an advantage in case of competition between individuals, it could be a disadvantage in competition between different kin groups, because the group with smaller members could produce more of them.

I also like pleiotropy and balanced effects based on gender.

By: Mike Keesey

Mike Keesey — Wed, 19 Oct 2011 22:58:01 +0000

"...why everyone should be tall..." Practically everyone is tall. Even pygmies. Look at Ardipithecus or Praeanthropus.