OK, so this statement is completely wrong, but it serves to illustrate the false conclusion of thinking that we are descended from chimpanzees because we evolved from an ape of some sort and they are our closest living relative. But we evolved from them no more than they from us.
What we do share is a common ancestor which we both descended from, and this makes chimpanzees our closest living cousins in species terms, but not our actual ancestors. Understanding common ancestors is vital to understanding evolution and classification, so lets go back in time to trace our little corner of the tree of life.
DNA analysis has shown that the ancestor linking us with chimps existed about six million years ago, and other evidence suggests it was certain to have lived in Africa. No fossil has been found that can be definitely attributed to it, but there are a few contenders. So, since we have no proper name let’s just call it ape A. But what did it look like? It would have been fairly close in appearance to a chimpanzee and it would have walked on four legs (using knuckle walking similar to chimps and gorillas), lived in the forest and been an excellent tree climber.
Around this time the climate began to cool a little and become dryer, meaning the forest in Africa began to thin out and in places open plain took over. This may have caused the population of ape A to become split into two, and therefore each group pursued it’s own independent evolutionary path. One group remained in the forest and so there were few external pressures for it to change – it would eventually evolve into chimpanzees. The other group must have come under some environmental pressure to cause it to change. This may have been a further thinning of the forest it was living in, but for whatever reason, it gradually evolved to become more adapted to living in the plains rather than the forest. This branch eventually became modern humans.
So ape A is the common ancestor we share with chimpanzees and makes them our closest living cousin within the animal world. It also means that the chimpanzee’s closest cousin is us, rather than any other ape. We have both had the same amount of time to evolve since ape A existed, but the reason we look so dissimilar is due to the different path that the environment led us to take – we took to the plains and became hunter gatherers instead of staying in the forests.
The next nearest living relative to us (and chimpanzees) is the gorilla and we need to go back 7 million years from present to find the ancestor we all share – call it ape B. Again it would have lived in the African forest and there would have been a split in the population somehow, one line leading to gorillas and the other to ape A, and subsequently to chimpanzees and us.
Going back even further, about 18 million years from present, we come across the common ancestor to all the great apes. Great apes comprise gibbons, orang utans, gorillas, chimpanzees and humans. They are a separate group from monkeys and the key difference is that apes have no tail whereas all monkeys do (though in a few it is almost reduced to nothing). This is a good illustration of how common ancestors are so useful in defining evolutionary paths and modern classification. If apes are defined as separate from monkeys due to their lack of tail (although it’s actually slightly more complicated than that), then this could be traced back to the one single species that lacked a tail and is ancestor to all subsequent apes.
All major groupings will have a single common ancestor at some point. So for example the first mammal species I talked about in a previous post would have had mammary glands, three bones in the ear, warm blood and fur – and this is why all mammals possess these and why we put them into a group separate from all other animals. As we go back in time there will be common ancestors to larger and larger groupings, until we reach that one first originator of all life with that one huge characteristic that all life shares – DNA.