October 20, 2011
Genes That Make Human Brain Distinctively Human

Why are humans smarter than other species? About 50 to 60 genes unique to humans are involved in building and operating the frontal cortex of the brain.

Young genes that appeared after the primate branch split off from other mammal species are more likely to be expressed in the developing human brain, a new analysis finds. The correlation suggests that evolutionarily recent genes, which have been largely ignored by scientists thus far, may be responsible for constructing the uniquely powerful human brain. The findings are published October 18 in the online, open access journal PLoS Biology.

"We found that there is a correlation between new gene origination and the evolution of the brain," said senior author Manyuan Long, PhD, Professor of Ecology & Evolution at the University of Chicago. "There are some 50 to 60 human-specific genes in the frontal cortex of the brain, the part that makes humans diverge with other non-human primates."

These genes are good candidates to compare people to identify the genes that cause IQ differences.

Here's the report: Accelerated Recruitment of New Brain Development Genes into the Human Genome

These genes express early in development:

The researchers found that a higher percentage of primate-specific young genes were expressed in the brain compared to mouse-specific young genes. Human-specific young genes also were more likely to be expressed in the recently expanded human brain structures, such as the neocortex and prefrontal cortex.

"Newer genes are found in newer parts of the human brain," said Yong Zhang, PhD, postdoctoral researcher and first author on the study. "We know the brain is the most remarkable difference between humans and other mammals and primates. These new genes are a candidate for future studies, as they are more likely to underlie this difference."

The timing of when the young human-specific genes are expressed in the brain also intrigued the researchers. Inspired by an ultrasound appointment with his pregnant wife, Zhang calculated when young genes were expressed in the human brain, discovering that they were more likely to appear during fetal or infant development.

The early activity of these genes suggests scientists should be looking at earlier developmental stages for genetic activity that ultimately shapes the complexity of the human brain.

These genes probably don't just play a role in boosting IQ. They might make unique human behaviors manifest as well.

Share |      Randall Parker, 2011 October 20 06:02 AM  Brain Intelligence


Comments
JP Straley said at October 20, 2011 6:58 AM:

"Young" genes may also be associated with the extraordinary lifespan humans display compared to other mammals?
JP Straley

Randall Parker said at October 20, 2011 8:54 PM:

JP,

That makes sense. Basically, any way we differ from other species stand a decent chance of being at least partially caused by new genes.

I'm curious to know how many new genes were formed from old genes recombining and how many from genes that jumped over from viruses.

Fat Man said at October 20, 2011 8:59 PM:

"extraordinary lifespan humans display"

Compared to what? What is the average life span of hunter gatherers who have no acess to modern medicine? 40 years? Whales can live for more than a century. Elephants in zoos lie quite a long time as well.

Brett Bellmore said at October 21, 2011 4:50 AM:

Fat Man, humans are something of outliers in terms of longevity, whether you're looking at longevity vs brain fraction, number of heartbeats, energy processed per kg over lifespan... There are a few species which have us beat, but not many.

Longevity seems to correlate with ability to avoid predation. Makes sense, if you're being eaten in your youth, you never get a chance to age, so why would evolution select against genes that promote fast aging? This suggests we're evolving longer lifespans now, not that it does any of us any good.

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