Getting a leg up during evolution

How did the human hand evolve? A Yale study in the July 3 issue of Cell describes some of the genomic changes that may have modified limb development during human evolution.

Using a biochemical marker, James P. Noonan, Ph.D., associate professor of genetics, and colleagues globally identified DNA sequences that promote and enhance gene expression in developing fore- and hindlimbs (or hands and feet) of mice, monkeys, and humans. They found that 13 percent of sequences have significantly increased activity in human limbs compared to monkey and mouse, gains pointing to over 300 genes that show increased expression in the human embryonic limb.

“It has been difficult to understand how human traits evolved, because we didn’t know where the important genetic changes might be,” Noonan says. “Now we do, and we have the tools to determine what biological effects these changes may have. Our study provides a roadmap for understanding other human-specific traits that arise during development, such as increased brain size and complexity.”