Big brain DNA found in humans: single gene that made us more intelligent than chimps is identified for the first time

Published: 23:38 p.m., 27 Febreuary 2015

Source: Ellie Zolfagharifard for mailonline.

Link: http://www.dailymail.co.uk/sciencetech/article-2972875/Big-brain-DNA-humans-Single-gene-intelligent-chimps-identified-time.html  

Science field: Medical investigation

Summary:

The ARHGAP11B gene increases the number of neurons in neocortex. This is a brain region that is key to reasoning, language and perception. Scientists believe the gene arose in humans after our ancient an ancestors and those of chimps split more than five million years ago.

Glossary:

-          Chimps: a chimpanzee.

-          Reasoning: the act or progress of drawing conclusions from facts, evidence, etc.

-          Ancestor: a person from whom someone is descended forebear.

-          Trigger: anything that causes a reaction.

-          Growth: the act or process or manner of growing.

-          Embryo: an animal in the early stages of development in the womb or egg.

-          Skull: the bony framework of the head.

Review:

While we share 99 per cent of our genes with chimpanzees, our brains are still three times as big. Scientists believe that during the evolution our genome must have changed in order to trigger such a massive brain growth. Now, for the first time, researchers have identified a gene that is only present in humans, making our minds far more complex than other species. The gene arose in humans after our ancient ancestors and those of chimps split from the same evolutionary path more than five million years ago. The gene contributes to the reproduction of basal brain stem cells triggering an increase in the number of neurons in the neocortex.

This is a brain region that is central to reasoning, language and sensory perception. Isolating different subpopulations of human brain stem cells we can identify which genes are active in which cell type.

Tests on mouse embryos revealed that the gene can have a huge impact on brain development. Embryos injected with the gene grew larger brain regions and some developed the wrinkled surface characteristic of the human brain, allowing more tissue to fit into the skull.

It is so amazing that one tiny gene alone may suffice to affect the phenotype of the stem cells, which contributed the most to the expansion of the neocortex. But it is likely this gene is just one of a large number of genetic changes that make human intelligence unique.

Around 3.8 million ago, our ancestors Australopithecus afarensis, had a brain that was less than 30 cubic inches (500 cubic centimetres) in volume. About 1.8 million years ago, Homo erectus had a brain twice the size of Australopithecus afarensis. When Neanderthals and Denisovans arrived, the brain had grown to 85 cubic inches (1.4 litres) in volume.

Despite this increase in size, human's intelligence may have more to do with how brain cells form that how large the brain grows. Now, the next step is the mice to grow into adults while carrying the gene to see if it improves their intelligence.

Written by Rebeca Mees