This is a question that one frequently encounters on various blogs. It expresses a desire to learn more about one’s origins, but reflects a misunderstanding of how science currently interprets these origins.
We are the only representative of the human lineage still around; the fossil record is replete with earlier hominids that did not survive. The same applies to the non-human portion of the Primate Order: some of them are around today, many more have become extinct.
So what is this business with a “common ancestor?” This expression refers to earlier forms we can trace our origins back to. Consider this image:
Starting at the bottom of the image, there are lines extending upwards, towards a number of branches, such as lemurs, New World monkeys, etc. The intersection of these lineages represents the place where speciation (or the evolution of a new species) occurred.
Let’s take humans and chimpanzees as an example.
At one point, there were no chimps or humans. This is where we place a common ancestor (in this example, we place its existence in the section following the branch leading up to gorillas and before the branching between chimps and humans).
Each of the animals identified is still with us today. As I mentioned in an earlier blog, we are all subject to continuous evolutionary pressures and development. As such, we can say that the monkeys with whom we share our world are not our ancestors, because we live side by side. However, we do share a common ancestor. From this common ancestor, branches lead to us and to other, non-human primates.
Go back to the image one more time. The further down the diagram you go, the further back in time you have traveled. So, looking at the image we can see that monkeys, apes and humans share a common ancestor, but that ancestor existed much earlier than the common ancestor between us and chimps.
Another way to address the question would be to point out that our “family history” is, in fact, “history.” It resides in the past. We cannot find ancestors among current (distant) relatives; we have to go back far in time to find them.