We Homo sapiens didn’t wont to be alone. Long ago, there was lot more human diversity; Homo sapiens lived alongside an estimated eight now-extinct species of human about 300,000 years ago. As recently as 15,000 years ago, we were sharing caves with another human species referred to as the Denisovans. And fossilized remains indicate a good higher number of early human species once populated Earth before our species came along.
“We have one human species right now, and historically, that’s really weird,” said Nick Longrich, an evolutionary biologist at the University of Bath in UK . “Not that far back, we weren’t that special, but now we are the only ones left.”
So, How many early human species were there?
When it comes to figure out exactly how many distinct species of humans existed, it gets complicated pretty quickly, especially because researchers keep unearthing new fossils that end up being totally separate and previously unknown species.
“The number is mounting, and it will vary depending on whom you talk to,” said John Stewart, an evolutionary paleoecologist at Bournemouth University in UK. Some researchers argue that the species referred to as Homo erectus is actually made from several different species, including Homo georgicus and Homo ergaster.
“It’s all about the definition of a species and therefore the degree to which you accept variation within a species,” Stewart said. “It can become a irritating and pedantic discussion, because everyone wants a solution . But the reality is that it really does depend.”
What is a species?
The definition of a species wont to be nice and simple: If two individuals could produce fertile offspring, they were from same species. as an example , a horse and a donkey can mate to supply a mule, but mules can’t successfully reproduce with each other. Therefore, horses and donkeys, though biologically similar, aren’t same species. In recent decades, however, that simplicity has given way to a more complex scientific debate about the way to define a species. Critics of the interbreeding definition means that not all life reproduces sexually; some plants and bacteria can reproduce asexually.
Others have argued that we should always define species by grouping together organisms with similar anatomical features, but that method has weaknesses also . There are often significant morphological variation between the sexes and even individuals of same species in several parts of the earth, making it a really subjective way of classifying life.
Some biologists like better to use DNA to draw the lines between species, and with advancing technology, they can do so with increasing precision. But we do not have the DNA of each ancient human — the genome of Homo erectus, as an example , has never been sequenced.
It gets even murkier once you consider that the maximum amount as 2% of the typical European’s DNA comes from Neanderthals and up to 6% of the DNA of some Melanesians (Indigenous people from islands directly northeast of Australia in Oceania) comes from Denisovans. So, are we a separate species from these ancestors?
“Some people will tell you that Neanderthals are same species as us,” Stewart said. “They’re just slightly different sort of modern humans and therefore the interbreeding is that the proof, but again the definition of species has moved on from just interbreeding.”
After taking all of this under consideration, some experts have argued that the concept of a species doesn’t actually exist. But others say that, while a cast-iron definition of a species is almost impossible to achieve, it’s still well worth the effort so that we can talk about evolution — including the evolution of our own species — during a meaningful way.
So we muddle on, knowing that a species means different things to different people — which suggests , of course, that people will disagree on how many species of human have ever existed. it is also a ques of what constitutes human. To answer this question, it helps to know the word hominin, a large group that has humans and chimps going back to their shared ancestor.
“The chimpanzee and us have evolved from common ancestor,” Stewart said. If we decide that humans are everything that arrived after our split from ancient chimpanzees about 6-7 million years ago, then it’s likely to be a various group. The Smithsonian National Museum of natural history has listed a minimum of 21 human species that are recognized by most scientists. Granted, it isn’t a completely complete list; the Denisovans, for instance, are missing.
Those on the list include Homo sapiens, Neanderthals, the Indonesian hobbit-size people, Homo erectus and Homo naledi. The list also includes other species that existed closer in time to the common ancestor of humans and chimps, then look more like chimpanzees than modern-day humans. Despite their looks, these species are still referred to as early humans. “You can’t go back 5 million years and expect them to seem like us,” Stewart said.
If the Smithsonian says there are 21, then you can be sure the diversity is much greater, Stewart said. That’s because the list errs on the side of caution, picking the species that are close to universally recognized. as an example , the recently discovered dwarf human species Homo luzonensis, who is known from just a few bones from a cave in Philippines, isn’t included on the Smithsonian’s list.
Researchers also suspect there are many other fossilized species yet to be excavated. “The list has only ever grown and that i don’t see why that will change,” Stewart said.