April 30, 2010

Humans and Chimps Not So Genetically Similar After All

April 29, 2010
Casey Luskin
Evolution News

Research published in Nature over the past few months is showing a much greater genetic distance between humans and chimps than previously thought, while revealing a closer one between humans and Neanderthals.

A Nature paper from January, 2010 titled, "Chimpanzee and human Y chromosomes are remarkably divergent in structure and gene content," found that Y chromosomes in humans and chimps “differ radically in sequence structure and gene content,” showing “extraordinary divergence” where “wholesale renovation is the paramount theme.” Of course, the paper attributes these dramatic genetic changes to “rapid evolution during the past 6 million years.”

One of the scientists behind the study was quoted in a Nature news article stating, "It looks like there's been a dramatic renovation or reinvention of the Y chromosome in the chimpanzee and human lineages." The news article states that “many of the stark changes between the chimp and human Y chromosomes are due to gene loss in the chimp and gene gain in the human” since “the chimp Y chromosome has only two-thirds as many distinct genes or gene families as the human Y chromosome and only 47% as many protein-coding elements as humans.” According to the news piece, “Even more striking than the gene loss is the rearrangement of large portions of the chromosome. More than 30% of the chimp Y chromosome lacks an alignable counterpart on the human Y chromosome, and vice versa, whereas this is true for less than 2% of the remainder of the genome.“

But not wishing to offend the “myth of 1%”, the Nature news article carefully adds, “The remainder of the chimp and human genomes are thought to differ in gene number by less than 1%.”

While this research takes us genetically further from apes, a more recent report in Nature news takes us genetically much closer to Neanderthals. Titled, “Neanderthals may have interbred with humans,” the article explains that “A genetic analysis of nearly 2,000 people from around the world indicates that such extinct species interbred with the ancestors of modern humans twice, leaving their genes within the DNA of people today.” According to this new article:

"[I]t may help explain the fate of the Neanderthals, who vanished from the fossil record about 30,000 years ago. 'It means Neanderthals didn't completely disappear,' says Jeffrey Long, a genetic anthropologist at the University of New Mexico, whose group conducted the analysis. There is a little bit of Neanderthal leftover in almost all humans, he says."

Given the high degree of skeletal similarity between humans and Neanderthals, the notion that we interbred is nothing new. They have been called a possible "race" of our own species, as studies have found their body shape is highly similar to that of modern human variation. Indeed, the discovery of "morphological mosaics" indicates that they likely interbred with modern humans. The finding of a modern-humanlike hyoid bone in a Neanderthal implies that they may have had language capabilities.

Textbooks often depict Neanderthals as primitive, bungling brutes with a vaguely human-like form (see above)—an attempt to instill the ape-to-human icon in students. But as Time Magazine reported in 1999, there’s increasing evidence showing that this evolutionary interpretation was wrong, and Neanderthals were essentially “all just people”:

"The real message, [a Washington University paleoanthropologist Erik] Trinkaus believes, is that to people living in the Stone Age, Neanderthals were just another tribe. 'They may have had heavier brows or broader noses or stockier builds, but behaviorally, socially and reproductively they were all just people.'" (Michael D. Lemonick, "A Bit of Neanderthal in Us All?," Time Magazine (April 25, 1999).)

Some ID proponents might disagree with me on this particular point, but it’s my view that Neanderthals were a race of human beings that ultimately went extinct. Either way, it’s becoming increasingly clear that Neanderthals do nothing to bolster the case that humans evolved from more primitive hominids.