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Humans evolved to be taller and faster-thinking


From ScienceDaily:

Those who are born to parents from diverse genetic backgrounds tend to be taller and have sharper thinking skills than others, the major international study has found.

But can we unharness the cart from the horse here? Wouldn’t smarter people be more likely to look to genuine advantage as opposed to narrow bigotry, when picking mates?

Researchers analysed health and genetic information from more than 100 studies carried out around the world. These included details on more than 350,000 people from urban and rural communities.

The team found that greater genetic diversity is linked to increased height. It is also associated with better cognitive skills, as well as higher levels of education.

It’s at least worth noting that small stature can be (but of course is not always) related to malnutrition, which is less likely among smarter people, given a chance.

Here’s the abstract:

Homozygosity has long been associated with rare, often devastating, Mendelian disorders1, and Darwin was one of the first to recognize that inbreeding reduces evolutionary fitness2. However, the effect of the more distant parental relatedness that is common in modern human populations is less well understood. Genomic data now allow us to investigate the effects of homozygosity on traits of public health importance by observing contiguous homozygous segments (runs of homozygosity), which are inferred to be homozygous along their complete length. Given the low levels of genome-wide homozygosity prevalent in most human populations, information is required on very large numbers of people to provide sufficient power3, 4. Here we use runs of homozygosity to study 16 health-related quantitative traits in 354,224 individuals from 102 cohorts, and find statistically significant associations between summed runs of homozygosity and four complex traits: height, forced expiratory lung volume in one second, general cognitive ability and educational attainment (P < 1 × 10-300, 2.1 × 10-6, 2.5 × 10-10 and 1.8 × 10-10, respectively). In each case, increased homozygosity was associated with decreased trait value, equivalent to the offspring of first cousins being 1.2 cm shorter and having 10 months’ less education. Similar effect sizes were found across four continental groups and populations with different degrees of genome-wide homozygosity, providing evidence that homozygosity, rather than confounding, directly contributes to phenotypic variance. Contrary to earlier reports in substantially smaller samples5, 6, no evidence was seen of an influence of genome-wide homozygosity on blood pressure and low density lipoprotein cholesterol, or ten other cardio-metabolic traits. Since directional dominance is predicted for traits under directional evolutionary selection7, this study provides evidence that increased stature and cognitive function have been positively selected in human evolution, whereas many important risk factors for late-onset complex diseases may not have been. (paywall) – Peter K. Joshi, Tonu Esko, Hannele Mattsson, Niina Eklund, Ilaria Gandin, Teresa Nutile, Anne U. Jackson, Claudia Schurmann, Albert V. Smith, Weihua Zhang, Yukinori Okada, Alena Stancáková, Jessica D. Faul, Wei Zhao, Traci M. Bartz, Maria Pina Concas, Nora Franceschini, Stefan Enroth, Veronique Vitart, Stella Trompet, Xiuqing Guo, Daniel I. Chasman, Jeffrey R. O’Connel, Tanguy Corre, Suraj S. Nongmaithem et al. Directional dominance on stature and cognition in diverse human populations. Nature, 2015 DOI: 10.1038/nature14618

All we really know about human evolution.

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Oh brother. Another attempt to say smarts comes from genes. then diversity in breeding. does history show this? No! we are taller now because we are healthier and should never of been that shirt. pygmy's were small because of bad health . nOt because of natural innate genes although it was passed from parents to kids. Robert Byers
Thanks, wd400, both of these posts are very helpful. daveS
What about the fact that many faster-thinking humans were not especially tall? How tall must one be if one is fast thinking?
There actually is a small correlation between height and intelligence in human populations. That's all this research would predict (since both are themselves correlated with homozgosity, something which in turn only explains a small amount of variance in either trait). Sp, I don't see a problem with your first sentence. The second sentence doesn't seem to make any sense. wd400
Hey Dave, I'm not sure abut "like a 5 year old" but how's this for an explanation. Long runs of homozogosity (having both copies of a bunch of genes be identical) are only a problem if one of two things are true. (a) Having two different copies of a gene is good. (b) If bad alleles are generally recessive The classic example of (a) is sickle cell anemia in Africa. It turns out such "heterozygous advantage" is not common enough to be the main reason homozgosity is a bad thing. It might not be as obvious why (b) would lead to homozygosity being a problem. But you have to remember that unsually high homozgosity in a population is the result of inbreeding (no necessarily cousin marriage -- just more inbreeding that you'd get in a large randomly mating population). With inbreeding individuals are likely to inherit the _same_ copy of a gene twice. That means there is not chance that recessive alleles have their effects masked by some other from. You might be wondering what this has got to do with selection. Well, selection can fix beneficial dominant alleles quickly (as they always display their trait). It's much harder to get rid of recessive alleles with deleterious effects because once they are rare they are always masked by a more-common dominant allele. Thus, when selection is operating on a trait you end up with "directional dominance" and most of the alleles that decrease fitness are recessive (and rare). That the pattern seen for height and cognitive ability but not most other traits. Deborah Charlesworth has a very nice review of the causes of inbreeding depression (the broader topic discussed here) if you want to read further. wd400
What about the fact that many faster-thinking humans were not especially tall? How tall must one be if one is fast thinking?
Maybe I'm missing something, but is there any implication in the paper that height and intelligence are positively correlated? I don't see any indication of that in the abstract. Based on a few tidbits I find via google, I'm guessing that positively selected traits can also be negatively correlated or even independent. daveS
What about the fact that many faster-thinking humans were not especially tall? How tall must one be if one is fast thinking? That is, it is much easier to see how selection would favour the fast thinker, in principle, than how it would favour the tall person in principle. Tallness imposes constraints that knowing how to solve a problem doesn't. News
(raises hand, in the spirit of a 5 year old) Umm, if height and intelligence are positively selected by evolution, why are we so much less physically robust than Cro Magnon? More to the point, what's up with our skulls being 15 percent smaller? anthropic
Could someone please explain this like I’m 5? Sure. Eat your vegetables davey, they're good for you. Or you won't get any dessert. Mung
Could someone please explain this like I'm 5? I'm having trouble understanding the reasoning. I'll take a stab: 1) Heterozygosity is associated with greater height and intelligence. 2) From the abstract: "Since directional dominance is predicted for traits under directional evolutionary selection". Does this mean that traits that appear in offspring of genetically dissimilar parents are generally positively selected? 3) Therefore 1) and 2) imply that greater height and intelligence have been positively selected. daveS

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