What makes modern humans unique is a question that has long eluded researchers. One way to approach the problem is to study proteins, or building blocks, in the body that have changed compared to our ancestors and that almost all living people now carry around. There are about a hundred proteins that have such a unique change. One of them is the protein glutathione reductase which is part of the body’s defense against oxidative stress (ie the overproduction of free oxygen radicals, ed.).
Now, researchers from the Karolinska Institutet and the Max Planck Institute in Germany have examined the change in glutathione reductase in detail and have been able to show that the Neanderthal protein created more reactive oxygen radicals. It is the third unique human change studied so far.
More common in India
The study also shows that the Neanderthal protein was passed on to living humans at low frequency when our ancestors mixed with them about 60,000 years ago. Today it occurs mainly in the Indian subcontinent (India, Pakistan and Bangladesh, editorial comment), where it is estimated that 1-2 percent carry the Neanderthal protein. The researchers found that the variant was associated with an increased risk of vascular disease and inflammatory bowel disease, both diseases linked to oxidative stress.
The increased risk we see is significant with increased risk of inflammatory bowel disease and vascular disease, says Hugo Seiberg, a researcher at Karolinska Institutet.
The explanation may be an increased life expectancy
Why this particular change has become one of the unique changes that almost all modern people carry, researchers have only theories.
The oxidative stress of braking is a bit like preventing something from rusting too much. Perhaps the fact that we are living longer is what prompted this change, speculates Svante Pääbo, a researcher at the Max Planck Institute.
Hugo Zeberg, Associate Professor, Department of Neuroscience, Karolinska Institutet, [email protected], Svante Pääbo, Director of the Max Planck Institute for Evolutionary Anthropology, [email protected]
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