Francis Blake London, UK
In order for there to be a genuinely separate species of human – one that could no longer successfully interbreed with Homo sapiens, which is a key definition of a separate species – two conditions would need to be met.
First, a part of the present population of humans would have to be physically isolated from the rest. Second, there would have to be sufficient evolutionary pressure on that isolated community. Then, given enough time, the genetic change in the isolated community might eventually lead to the formation of a new species. However, humans were isolated in Australia for at least 50,000 and possibly as much as 125,000 years, and yet they remained the same species as those in the rest of the world.
Hanno Schmidt Mainz, Germany
It wouldn’t be exceptional to have more than one species of humans on this planet, because this was the case over most of the time of our existence. The last “sympatric” humans we know of were Neanderthals, who became extinct only about 30,000 years ago.
Since stable separation of parts of the species is the key factor for the formation of new species, we can say that a new split of our species is impossible under current circumstances. We are globally connected as never before and this trend is accelerating.
However, we can still play “what if?”. The only realistic scenario for the evolution of two species out of ours would probably be if we expanded beyond our home planet and then lost contact with the settlers. If both populations survived long enough – much more than 100,000 years – we might see divergence and maybe two species of humans.
Mike Follows Sutton Coldfield, West Midlands, UK
We might get the evolution of new human species if we colonise other planets where people have to adapt to an alien environment.
Mars, for example, is further away from the sun so residents there may evolve bigger eyes to see better in the dimmer light. And without life, Mars is essentially a sterile environment and this may make Martian colonists more susceptible to disease so that mixing with people on Earth is discouraged. This could rule out sex and increase the chance the colonists would develop into a new species.
However, such speciation might happen if we stay on Earth too. If scientists mastered germline therapy, a person’s genome could be manipulated. This might bestow an advantage like longer life to the individual and their children. This therapy would probably only be available to wealthier people who might tend to pair up with other “enhanced” individuals, perhaps eventually leading to a new species. This process is started artificially by tinkering with genes, but reinforced and consolidated by cultural differences. This might be in the realms of science fiction at the moment, but it wouldn’t be the first time that science fiction became science fact.
Herman D’Hondt Sydney, Australia
Of course it is possible, but I feel strongly that it won’t happen.
Homo sapiens split from Neanderthals at least 400,000 years ago, when Neanderthals moved into Europe and Asia,
while H. sapiens stayed in Africa. Yet, when the two subspecies met again hundreds of thousands of years later, they were still able to interbreed. Even if we could spread to other planets and interstellar travel took thousands of years, this is still a short period compared with the time required for the evolution of new species.
Ben Haller Ithaca, New York, US
One obstacle is that selection due to environmental differences has largely ceased to operate in humans today. Earlier in our evolutionary history, our survival would have depended on our degree of adaptation to local environmental conditions, but culture and technology have now largely mitigated that.
For an interesting exploration of these ideas, try The Time Machine by H. G. Wells. Published in 1895, it is one of the earliest examples of the genre of science fiction, and remains a classic.