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Did More Than One Human Species Exist on Our Planet? DNA Sequencing May Give the Answer

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Last Updated: January 25, 2021, 15:00 IST

Image for representation purpose only. Credits: Rowan Millar / Flickr

Image for representation purpose only. Credits: Rowan Millar / Flickr

Figuring out exactly how many human species existed the planet at one time is not an easy task. We only have fossilised remains to track the number and the search for fossils is never-ending.

When we think of humankind, we assume Homo sapiens, i.e., us, are the only ones who quantify as human beings. However, if you hold that assumption, you might be surprised to know that it’s not true at all. We are not the only ones who evolved from tree-dwelling animals to bipedal social creatures. However, we are the only ones that are left from that group, the only survivors. Not long ago, if you assume 300,000 years ago is not that long, there were at least 8 different types of humans who existed on this pale blue dot that we call our home, planet earth.

In an interview with Live Science, evolutionary biologist Nick Longrich from the University of Bath in the United Kingdom noted it was weird that we have only one human species now. Before our species came along, a wide variety of human species populated Earth.

Figuring out exactly how many human species existed the planet at one time is not an easy task. We only have fossilised remains to track the number and the search for fossils is never-ending. Every now and then, some new fossil is uncovered which doesn’t match any of the previously known human species.

We come under the genus Homo, and our species is Sapiens. A species is defined when two members of the group can successfully make an offspring, whereas members of the same genus do not. Some biologists disagree and say we should classify a species simply based on anatomical features. Other schools suggest DNA should be the only deciding factor when it comes to naming species.

Once other species existed within this genus, Homo. John Stewart, evolutionary palaeoecologist, says the number will differ based on the scientist you talk to. There is a school of thought that even suggests Homo erectus is in fact made up of several different species, including Homo georgicus and Homo ergaster.

It gets really murky to identify which humans would quantify as a different species because of a lack of DNA sequencing. Denisovans and Neanderthals are recognised as human species but they have never been sequenced. But some argue that Neanderthals are simply our ancestors and not a separate species.

Also Read: Climate Change Did Not Drive Neanderthals of Western Mediterranean to Extinction

Therefore, some experts believe speciation from an evolutionary standpoint is impossible to classify when it comes to humans. With various sects differing on the meaning of the word species itself, it is hard to exactly list how many human species existed. Some move back to the hominin family. It was the hominin group where our shared ancestor with Chimpanzee separated.

Considering our last common ancestor split 6 million to 7 million years ago, it must have been a very diverse group then. According to Smithsonian, there are 21 recognised human species. But other papers list only 10-12 species as humans. Some lists don’t include Denisovans while some don’t have Homo naledi, a hobbit-sized human species discovered in Indonesian caves. This might be because they look more like chimpanzees than us. But Stewart explains it as, “You can't go back 5 million years and expect them to look like us,” and argues they are early humans.

In conclusion, though the exact number remains unknown, the human species were much more diverse than considered by most.

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