we Homo sapiens He never used to be alone. Long ago, there was a lot of human diversity. Homo sapiens He lived side by side with what he estimated Eight species are now extinct About 300,000 years ago. As recently as 15,000 years ago, we were sharing caves with other human species Known as Denisovans. Fossil remains indicate a greater number of early human species that inhabited the Earth before the emergence of our species.
“We have one human species now, and historically, that’s really strange,” said Nick Longreach, an evolutionary biologist at the University of Bath in the United Kingdom. “It wasn’t far away, we weren’t special, but now we are the only ones left.”
So how many early human species were there?
When it comes to figuring out how many distinct species of humans are, the matter becomes complicated very quickly, especially because researchers continue to discover new fossils that end up being completely separate and previously unknown species.
“The number is growing, and it will vary depending on who you talk to,” said John Stewart, an evolutionary paleontologist at Bournemouth University in the United Kingdom. Some researchers argue that the species known as Standing man It actually consists of several different types, including Homo gorgicus And the Homo ergaster.
“It’s all about defining the type and the degree to which you accept variation within a species,” Stewart told Live Science. “It can become a bit annoying and clumsy debate, because everyone wants an answer. But the truth is, it really depends.”
What is the type?
The definition of the species was gentle and simple: if two people could produce fertile offspring, they would both belong to the same species. For example, A. horse And a Donkey They can mate to produce a mule, but mules cannot successfully breed with each other. Therefore, horses and donkeys, although biologically similar, are not of the same species. But in recent decades, that simplicity has given way to a more complex scientific debate about how to define species. Critics of the definition of crossbreeding point out that not all life reproduces sexually; Some plants have bacteria It can reproduce asexually.
Others have argued that we must define species by grouping organisms with similar anatomical characteristics together, but this method also has weaknesses. There can be significant morphological difference between the sexes and even individuals of the same type in different parts of the world, which makes it a very subjective way of classifying life.
Some biologists prefer to use DNA To draw the lines between species, and as technology advances, they can do so with increasing precision. But we don’t have the DNA of every ancient human – a genome Standing manFor example, it was never serialized. I mentioned Live Science earlier.
It gets even more blurry when you think about it as much 2% of the average DNA of Europe comes from Neanderthals And up to 6% of DNA Some of the people of Melanesia (indigenous people from the islands northeast of Australia in Oceania) come from Denisovan. So, are we beings separate from these ancestors?
“Some people will tell you that Neanderthals are of the same species as us,” Stewart said. “They are just a slightly different species of modern humans and crossbreeding is the evidence, but again, the species definition has moved on from mere crossbreeding.”
After taking all this into account, some experts They argued that the concept of gender does not really exist. But others argue that while defining a type of cast iron is nearly impossible, it is still worth the effort so we can talk about it. has evolved – including the evolution of our species – in a meaningful way.
So we’re getting confused, knowing that species mean different things to different people – which means, of course, that people will disagree about how many human species have ever existed. It is also a question of what constitutes a human being. To answer this question, it helps to understand the word hominin, a large group that includes humans and chimpanzees that date back to their common ancestors.
“The Chimpanzee “We evolved from a common ancestor,” said Stewart. If we determine that humans are all that arrived after we separated from ancient chimpanzees about 6 million to 7 million years ago, it would likely be a diverse group. Smithsonian National Museum of Natural History Listed at least 21 human species Recognized by most scholars. True, it is not a complete list; Denisovans, for example, are missing.
Those in the list include Homo sapiensNeanderthals, and People of the Indonesian HobbitAnd the Standing man And the Nalidi man. The list also includes other species that existed sooner to the common ancestor of humans and chimpanzees, and thus are more similar to chimpanzees than humans in the modern era. Despite their appearance, this species was still known as early humans. “You can’t go back 5 million years and expect them to be like us,” said Stewart.
Stewart said that if the Smithsonian Institution says there are 21, then you can be sure the diversity is much greater. That’s because the list errs on the side of caution, choosing varieties that are close to universally recognized. For example, the recently discovered dwarf human species Homo lusonensisKnown from a few bones discovered in an Indonesian cave, it was not included in the Smithsonian’s list.
Researchers also suspect that there are many other fossil species that have yet to be excavated. “The list has only grown and I don’t see why that will change,” said Stewart.
Originally published on Live Science.
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