Early Human Species: How Many Were There?

It's no secret that homo sapiens aren't the only humanoid species in our history. But, exactly how many early human species were there? It really depends on how 'species' is defined.

History of the Human Species

Homo sapiens weren't always the only human species on Earth. A long time ago, there was more diversity in the human species. Records show that homo sapiens lived alongside roughly eight now-extinct humanoid species estimated 300,000 years ago.

Fairly recently, 15,000 years ago, homo sapiens lived and shared caves with other Denisovans human species. Unearthed fossilized remains prove that there is an even higher number of early humanoid species that roamed the Earth before our species came along.

Nick Longrich, an evolutionary biologist from the University of Bath in the U.K, says, "We have one human species now, and historically, that's really weird. Not that far back, we weren't that special."

The question now is, exactly how many early humanoid species were there?

Diversity of the Human Species

Determining the exact number of human species that existed is complicated mainly due to researchers constantly unearthing new fossilized remains that are separate from previously known species.

John Stewart, an evolutionary paleoecologist from Bournemouth University in the U.K, explains, "The number is mounting, and it'll vary depending on whom you talk to."

According to Stewart, researchers argue to this day that the known Homo Erectus is actually a group of several different species that include Homo ergaster and Homo georgicus.

In an interview with Live Science, Stewart says that the conflict stems from how the term 'species' is defined and up to what degree one accepts variations within a species. 

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What is a Species?

Before, the term 'species' was relatively easy to define. If two specimens could produce fertile offspring, they were part of the same species.

However, as science evolves, the simplicity of 'species' has given way to a complex scientific debate on the definition. Some critics point that not all species interbreed sexually, such as plants and some bacteria that reproduce asexually.

Others say that species should be group organisms with similar anatomic features, but it still failed to please all arguments. 

On the other hand, biologists prefer to use DNA sampling to draw the lines between species. Thanks to the advancements of technology, scientists today can do this with precision. However, there are not many early human DNA samples, which makes it even more difficult to draw the line between one human species and another.

It gets even more complicated when you consider that 2% of European DNA came from Neanderthals while 6% for some Melanesians come from Denisovans.

The Smithsonian National Museum of Natural History has published at least 21 humanoid species recognized by most scientists. However, it still doesn't host a complete list since it has no Denisovans and other humanoid species.

Stewart points that despite settling on the definition of 'species' seems mundane; it is vital for researchers and scientists to further understand how the evolution of the human species took place.

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