Science News Review

New Light Shed on Human Evolution

Nov 22 at 2:02pm by Aileen

There have been quite a few recent news reports about research shedding new light on human evolution. Some of it’s in the realm of those interminable Just-So stories biologists never seem to tire of (despite the notable fact that those Just-So stories change regularly according to who’s doing the storytelling today), but some of it’s darned good science.

First up is the newer, better Tale of The Simple Reason Helps Males Evolve More Quickly than females. This one’s particularly entertaining, as Just-So stories go. It comes from researchers at the University of Florida Genetics Institute, to be published in the Proceedings of the NAS. Spokes-researcher Marta Wayne explains it thusly:

“It’s because males are simpler.”

Well Duh. Of course, Wayne explains the long known fact that male inheritance involves simpler genetic architecture as compared to females. No doubt such as the fact that a woman gives birth to the female’s contribution to genetic inheritance of her granddaughters when she gives birth to a daughter. But you’ve just gotta love the conclusion, drawn from research on the ubiquitous fruit fly:

“Researchers believe this relatively uncomplicated genetic pathway helps males respond to the pressures of sexual selection, ultimately enabling them to win females and produce greater numbers of offspring.”

See? Very simple reasoning by those very simple males. Who said biological processes were highly complex?

More interesting (if you’re following the science) is the finding by researchers at UC Santa Cruz that Ancient Retroviruses Spurred Evolution of Gene Regulatory Networks in Humans and Other Primates. This quantifies part of the estimated 8% of the human genome that consists of endogenous retroviral DNA insertions.

This research highlights relatively recent knowledge that gene regulation - controlled by “master gene regulators” orchestrate gene expression profiles in higher vertebrates. By virtue of these expression networks species that have very similar genomes - like humans and chimpanzees - can still exhibit striking morphological differences.

The retroviral elements - “jumping genes” - jumped into new positions throughout the human genome and spread numerous copies of repetitive DNA sequences that allowed the master regulators to extend their networks. The researcher further found that these changes occurred only in the primate lineage through retroviruses that were primate specific, and are not found in mice.

As has become usual of late, the researchers conclude that their findings challenge the status of so-called “junk DNA,” which may not be nearly so junky as previously assumed. The research also challenges conventional evolutionary wisdom that small changes - point mutations - in the genetic code are the driving force of evolution. It now appears that there is a whole other level of evolution that occurs via changes to gene regulation and expression. Very interesting indeed!

Finally, research from the University of Toronto’s Centre for Cellular and Biomolecular Research has revealed more about why humans differ so much from chimpanzees despite their 99% identical genomes, in Humans and Chimps Differ At Level Of Gene Splicing.

The differences now appear to reside not in the DNA coding for proteins, but in how the genetic material is spliced to create proteins. Splicing is how the coding regions of genes are joined to create specification for protein synthesis. Splicing can occur in alternative ways, allowing the same DNA to generate more than one type of protein. These new findings show that the alternative splicing process differs significantly between humans and chimpanzees.

Now, THAT is very interesting too!

Links:

Simple Reason Helps Males Evolve More Quickly

Ancient Retroviruses Spurred Evolution of Gene Regulatory Networks in Humans and Other Primates

Humans and Chimps Differ At Level Of Gene Splicing