Evolution and human: having proper feet (Evolution)

by David Turell @, Wednesday, January 20, 2016, 14:24 (789 days ago) @ David Turell

Upright walking which only we do requires a specialized foot with the big toe properly aligned. A change in gene expression provided for them:


"It's somewhat unusual to have a research project that spans from fish all the way to humans, but it's clear that tweaking the expression levels of molecules called bone morphogenetic proteins can result in significant changes not just in the skeletal armor of the stickleback, but also in the hind-limb development of humans and primates," said David Kingsley, PhD, professor of developmental biology at Stanford. "This change is likely part of the reason why we've evolved from having a grasping hind foot like a chimp to a weight-bearing structure that allows us to walk on two legs."


"The researchers identified the area of the genome responsible for controlling armor plate size, and then looked for differences there in 11 pairs of marine and freshwater fish with varying armor-plate sizes. They homed in on a region that includes the gene for a bone morphogenetic protein family member called GDF6. Due to changes in the regulatory DNA sequence near this gene, freshwater sticklebacks express higher levels of GDF6, while their saltwater cousins express less. Strikingly, marine fish genetically engineered to contain the regulatory sequence of freshwater fish expressed higher levels of GDF6 and developed smaller armor plates, the researchers found.


"They began by working with colleagues in the laboratory of Gill Bejerano, PhD, Stanford associate professor of developmental biology, of computer science and of pediatrics, to compare differences in the genomes of chimps and humans. In previous surveys, they found over 500 places in which humans have lost regulatory regions that are conserved from chimps and many other mammals. Two of these occur near the GDF6 gene. They homed in on one in particular.

"'This regulatory information was shared through about 100 million years of evolution," said Kingsley. "And yet, surprisingly, this region is missing in humans."


"The fact that humans are missing the hind-limb-regulatory region probably means that we express less of the gene in our legs and feet during development, but comparable amounts in our nascent arms, hands and skulls. Loss of this particular regulatory sequence would also shorten lateral toes but not the first toe of feet. This may help explain why the big toe is aligned with other short, lateral toes in humans. Such a modification would create a more sturdy foot with which to walk upright.

"'These bone morphogenetic proteins are strong signals for bone and cartilage growth in all types of animals," said Kingsley.

"'You can evolve new skeletal structures by changing where and when the signals are expressed, and it's very satisfying to see similar regulatory principles in action whether you are changing the armor of a stickleback, or changing specific hind-limb structures during human evolution.'"

Comment: Chance or advanced planning? If God guided evolution this shows how He might have engineered it.

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