Because you are a human. Okay, but what is a human? Well, it’s a species of animal. Okay, then what is a species?
The most common definition on a species is known as the Biological
Species Concept (BSC).
Biological Species Concept – If two organisms can reproduce to produce fertile offspring, then they are the same species.
You cannot breed with a cow to produce fertile offspring. So, you and a cow are different species.
But deciding whether or not an animal is a different species is not always so clear.
The philosopher Henry Taylor and the biologists Jerry Coyne have both written articles on their take of what is a species.
Here is my take on if what a species is and whether it is useful.
For many animals this BSC definition works perfectly well. Cats can reproduce with dogs, so they are two different species. Homo sapiens can’t reproduce with chimps to produce fertile offspring. So chimps and humans are different species.
Okay, simple problem solved. Well no, it’s not quite that simple.
In Western Europe there is the carrion crow, in eastern Europe there is the grey hooded crow. In Germany there is a small point where these two birds and sometimes they can mate with each other to produce fertile offspring!
So, our concept of a species has fallen apart, there is no such thing as a species. Well again no, it’s not quite that simple.
All animals are constantly evolving, it just takes a really long time. In this crow case, the birds are in the process of speciation, but they are not quite as far a long in the process as say humans and chimps
So we have seen a case where it appears species exist and one where it is not quite so clear.
So, does this concept of a species actually exist? And is it useful?
No and yes.
I don’t think the concept of species exist as a universal truth.
Our efforts to categorise the natural world are just that, our efforts. They are not a biological or universal truth and we should do well to remember that. We are just trying to find order to the chaos.
However, I do think the concept of species is very useful. Especially in maintaining biodiversity to provide ecosystem services or in the development of new medicines.
Conclusion
I think we biologists view the concept of a species too strongly and inflexibly. Using it as a tool to understand the world is great but I think when categorising species it’s important to remember that it is a means to an end, rather than an end itself.