Human evolution: genetic source of upright posture (Introduction)

by David Turell , Friday, July 21, 2023, 23:18 (281 days ago) @ David Turell
edited by David Turell, Friday, July 21, 2023, 23:26

Latest massive study:

https://www.nature.com/articles/d41586-023-02345-7?utm_source=Nature+Briefing&utm_c...

"Humans are the only great apes to routinely walk on two legs, a posture that relies on us having long legs, short arms and narrow hips. A study, published this week in Science, has generated a map of genomic regions that could explain how our unique skeletal architecture evolved. The work also points to regions of our DNA that place us at risk of the common skeletal disease osteoarthritis.

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"Narasimhan and his colleagues turned to the UK Biobank, a repository of genetic and health data for half a million people, to obtain records that included whole-body X-ray images. They used artificial intelligence (AI) to weed out images that couldn’t be used in the analysis, such as blurred pictures and those of people with implants or amputations. They then applied further rounds of AI analyses to extract precise measurements of bone lengths from more than 31,000 records.

"Visscher says that the paper is “a real tour de force and clever use of computational deep-learning methodology”.

"The genome-wide map that Narasimhan and his colleagues generated identified 145 genetic locations associated with changes to skeletal proportions. Many of the identified regions are known to have roles in skeletal development and 45 of the locations overlapped a single protein-coding gene. Of those, 32 have previously been identified as resulting in abnormal skeletons when disrupted in mice, and 4 as causing rare skeletal diseases in humans.

"The team investigated a range of skeletal ratios, such as hip width to shoulder width, forearm length to height, and torso length to leg length. Limb and torso proportions were linked to distinct regions of the genome, suggesting that their development is controlled by separate genetic programs.

"Having longer legs than arms is a hallmark of walking upright, and genomic regions linked to changes in this ratio were different to similar regions in other great apes, a sign that these regions were under evolutionary selection in humans. The same was true for regions linked to narrow hips relative to overall height.

"One theory for why early hominins evolved upright walking is that their bodies were better able to keep cool in hot environments. Using biobank data on metabolic rate and body mass, the researchers found support for this hypothesis: as leg length increases, heat dissipation to stay cool improves. “There is this correlation between skeletal proportions and metabolic rate and fat-free body mass, which is in line with what the theory would predict,” says Narasimhan.

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"Bo Xia, a genomics researcher at Harvard University in Cambridge, Massachusetts, says that further work to identify the genetic elements responsible is needed, but will be challenging. Genome-wide association studies are powerful tools for identifying candidates for future research, he says, but pinpointing which genes directly affect the developmental processes is not straightforward if genetic variation occurs outside gene-coding sequences. “A non-coding region mutation near a specific gene doesn’t necessarily indicate that the variant is affecting the gene that’s close to it,” he says."

Comment: A previous paper presented here described HAR's, regions of DNA with accelerated changer toward an evolving sapiens form (Friday, August 14, 2020, 22:11). I wonder if the regions described here are comparable in DNA 3-D geography. The theory about long legs keeping an animal cooler should also be applied to apes and monkeys. If beneficial why didn't their legs lengthen like ours did? Pure Darwinist 'just so' silly thinking to explain away our obvious favorable differences in evolution.