This article does a very good job of articulating an argument that I presented a long time ago about speciation and evolution, and can be applied backwards to homo sapiens and our ancestors as well.

It quite clearly states:
Of course, it’s at this point that I have to mention that while I have talked about “dogs” this entire time, they’re not actually a different species. Wolves are Canis lupus, while dogs are merely a subspecies of wolves, Canis lupus familiaris. Despite centuries of selective breeding and the vast array of physical differences, dogs are still able to breed with their ancestors.

If you read between the lines of the rest of the article, other things also fall into place. There is no actual NEED for different species of Homo to have ever existed at all. In fact, it is much more like that there is now, and only ever has been, precisely one human species. The different skull shapes and modes of movement and all of that are cosmetic, for lack of a better term, the same as the size of the chihuahua, the skull of the pug, or the fine lines of a grey hound. We can also use them as a basis for understanding that different hunting/gathering patterns also do not reflect any real form of speciation as illustrated by the different groups of dogs in Moscow.

So again, if all dogs are still inter-breedable with their ultimate ancestor of the wolf, despite all of the physiological and psychological differentiation, where do we truly draw the line between species, and are there any examples of creatures that we can prove break that barrier.

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What is the purpose of living? How about, 'to reduce needless suffering. It seems to me to be a worthy purpose.