Evolution Yet Again: “If humans evolved from apes, why are there still apes?”

(continuation of this post)

Yes, my dad used to say this, and according to biologists who try to talk to the public about evolution, he is (was) far from being alone; (see: Richard Dawkins, The Greatest Show on Earth)

If this question makes you scratch your head in wonderment “who in the world would ask such a mind numbingly idiotic question?” take a look at what the public sees, even in some science museums:


Needless to say, this picture “explanation” is no explanation at all, and it is highly misleading. It starts with an ape like creature and shows a nice, straight line progression to a modern human.

When I saw this as a kid, my question was: “WHY did the species ever start to change to begin with?” This was a bit like “you don’t see an ape mother giving birth to a human kid!” (yes, adults do actually say that…)

The “why is there change at all question” is a different topic; one has to remember that we pass along our genes when we reproduce and, on rare occasions, there is a gene “copy error” (e. g., mutation). Though most mutations are harmful, a few are beneficial with respect to reproductive success and these are more frequently passed on than other genes. A few mutations are neutral (with respect to reproductive success) and some of these are also passed on. Eventually the variation of the frequency of the various types of genes changes and, over time, the distribution of the types of genes within a population changes. THAT is evolution.

But back to the “ape to man” picture: this is true, if one follows a very select trajectory along the tree of life. However the tree of life is very complicated. A rough sketch of the branches that includes humans looks like this:


So the accurate thing to say is that “modern chimps and humans have a common ancestor” (you have to follow the paths from the humans backward until it first meets the brach that ends with modern chimps). So this schematic, while more accurate, is still misleading. When you had that population from which modern chimps and modern people sprang, you didn’t start two nice straight segments, but rather new trees in and of themselves. So that “straight line” from that branch point to humans actually looks more like this, which is still highly simplified: (Smithsonian):


As you can see, there were many different types of hominins which went extinct. There were intermediates which were our ancestors, but there were other branches which went in a different direction and then went extinct. These beings were NOT our ancestors but rather cousins to our ancestors.

Think about it: when there is a branching (speciation), you don’t just get two straight lines…but over time you get two “subtrees” complete with lots of different branches, subbranches etc.

The “ape to man” drawing above describes just one (out of many) path from the common “chimp and human” ancestor to the present day; there are many other paths along this tree of life.

(note: my favorite books on evolution are:
Greatest Show on Earth (Dawkins…no worries; this is not about religion)
Why Evolution is True (Coyne)
Your Inner Fish (Shubin)
Science on Trial: The Case for Evolution (Futuyma) Professor Futuyma’s book is dated, but still a pretty good introduction.

Note: all of these books are written by top flight researchers who are gifted writers as well.


January 8, 2013 - Posted by | books, evolution, science, social/political |

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