What separates us from other primates is our larger brains. When we evolved from non-human primates, there was one specific human gene, which made our brains bigger while theirs remained smaller. Now, scientists used that same gene to grow a bigger monkey brain for the first time.
The experiment, published on June 18 in Science, was carried out by researchers from the Max Planck Institute of Molecular Cell Biology & Genetics in Germany, and the Central Institute for Experimental Animals in Japan.
Wieland Huttner of the Max Planck Institute, who led the study, said:
We had certain hopes — what the gene, ideally, could do and should, if it had the function that we had postulated it should have. The very satisfying answer is that the gene did exactly everything that you could have hoped for.
When the scientists inserted the gene, the results showed:
- An increase in the size of the monkeys’ neocortex.
- Folding of the monkey’s brain was induced, similar to how a human brain is folded.
- There was an increase in related pro-generative cell type, which produces neurons.
- It increased upper-layer neurons, which are the same neurons that rose during the evolution process.
Huttner concluded:
We confined our analyses to marmoset fetuses because we anticipated that the expression of this human-specific gene would affect the neocortex development in the marmoset. In light of potentially unforeseeable consequences with regard to postnatal brain function, we considered it a prerequisite – and mandatory from an ethical point of view – to first determine the effects of ARHGAP11B on the development of fetal marmoset neocortex.
When working with and on animals, ethical questions arise. Both Japan and Germany have high ethical standards and regulations regarding animal research and animal welfare. For this reason, the international team unanimously agreed to remove the fetus at 101 days (50 days before the regular birth date) through a C-section. The fetus samples were then sent from Japan to the MPI-CBG in Dresden, Germany, for detailed analysis.
