Human Genome Meeting,
Edinburgh, April 2001
Humanity: its all in the mind
Genetic activity in the brain gives us the edge over chimps.24 April 2001
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The difference between chimps and humans is all in the mind. It is differences in our brain's gene activity that really sets us apart from chimps, delegates at the Human Genome Meeting in Edinburgh, Scotland, heard this week.
"I'm interested in what makes me human," explains Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. After sequencing 3 million letters of the chimp genome and comparing them with the human draft, his group reasoned that DNA sequence can't be it: only 1.3% of letters are different.
So using tiny 'gene chips' with 20,000 human genes dotted on them, they measured the levels of gene activity, or 'transcription', in our brain, liver and blood. They compared these transcription snapshots -- the 'transcriptome' -- with similar snapshots of our close relative the chimp and an evolutionarily more distant relative, the rhesus macaque monkey.
"Liver and blood reflect how the species are related," Pääbo found. In these tissues, as expected, the human gene activity pattern was pretty similar to that of the chimp, and different from the macaque.
The brain showed a different picture: chimp and human transcription patterns are poles apart. "The [human] brain has accelerated usage of genes," explains Paabo.
The genomes of all mammals are so similar that "it's hard to understand how they can produce such different animals", says Sue Povey, who works on human gene mapping at University College London in England. If their genes are alike, it's probably changes in when, where and how active they are that drives the differences between species, she agrees.