Natural Selection

Evolution: the naughty word of the American Fundamentalist churches.  

Evolution is the process of moving from one state to another.  It can be applied to many different generals of information.  Often people state that some aspect of themselves evolved into another.  Sometimes it is a personal morality that evolves or a society that evolves, usually into something better.  Often this theme is applied to Biology as well and this would be grossly incorrect.  

Almost everyone in the world that knows a little about the Evolution, the theory of Evolution, thinks that it was invented by Charles Darwin.  Indeed many people, Fundamentalists or otherwise call it Darwin's Theory of Evolution.  I think the Fundamentalists point this out because Darwin was just a man and men commit errors, God does not.  But the theory of evolution was old before Charles Darwin was born.  As with many parts of science there was some Greek Dude that thought that things evolved from one thing to another, but he got almost everything wrong and it was not until the 1700s that serious thought was put into the subject.  What Darwin did was suggest the mechanism.

He did it quite well.  The mechanism is called Natural Selection.  Simply put, the animals that are best suited to survive at the time that they live are able to spread more of their genes to the next generation.  Meaning that the conditions in the natural habitat set the obstacles for life and the individuals in any given species that are best suited to that habitat are able to survive and pass more of their genes to the next generation than some individual less suited.  This means that the most successful individuals would pass on what makes them so successful to the next generation and their offspring would have a jump on the competition, assuming that the conditions persisted the same from one generation to the next.  

This of course does not apply to Humans.  Our society has become so large that it has ceased to be affected by natural selection mechanisms; we have social selection mechanisms and the passing of genetic material is not as important and passing on our values and our nurturing practices.  Indeed many of our practices and values are counter to the natural laws.

In animals and humans before we invented society, evolution by natural selection is the principal mechanism for change do species.  How does this work?  There are some important facts to understand.  There is never a start nor end of a species, except when the last of a species dies and then it has ended.  All change is gradual, it does not happen quickly by any stretch of the imagination.  The speed of evolution is tied to the length of a species' generation.  Humans evolve slowly because our generations are so long.  Single celled organisms evolve quickly because each generation is measured in minutes.  

A species is defined as a group of individuals with a similar appearance and importantly can breed together with viable offspring.  All dogs can breed, and often do, with each other and have fertile offspring.  Horses and donkeys can breed, but the offspring, Mules, are sterile.  What makes up a separate species is often up to interpretation.  Dogs can breed with Wolves and Coyotes, but all three are considered separate.  It may be that those three species did not share the same living space until recently and so opportunity to breed did not occur.  

What is a human?  That question in the past was defined as us.  That we evolved in Africa over the past few hundred thousand years and that was all.  Now we know, thanks to DNA, that there were a total of four types of Humans outside of Africa and one of them, us, bred with at least two of the others and likely the fourth as well.  This means that the Neanderthal man was closely related to humans.  So the question is that since Homo Erectus, one of the fossil species of man, existed at the same time as Neanderthals and our species for a bit, did we or the Neanderthals breed with them?  And the answer was probably, at least for the Neanderthals, yes.  

You see the way evolution works is through tiny changes from one generation to the next.  The other thing to know is that, it has not stopped.  You can only detect superficial changes between one generation and another.  One can only detect minor superficial changes between ten or one hundred generations.  Even a thousand generations most of the differences between present species and one a thousand generation ago are only superficial and the changes are more than superficial two thousand generations ago, but to the one thousand generation animal the two thousand generation and the zero generation animal are equally superficial in differences to it.  But it may be that we would need more than ten thousand generations difference before the two different animals would not be able to breed and likely much more.  Ten thousand human generations would only be about 150-200 thousand years and Neanderthals were thought to have branched off our ancestors more than twice that time ago and we were still compatible.  

Forks in the road.

When people draw diagrams of humans and other great apes we often see that chimpanzees and humans are closely related and we are attached to them with a two pronged pitch fork, one tine in the chimp and one in the man with the handle going to another divide.  It looks like that in that past time humans and chimps split off and there were separate from the start; this is what it looks like but it is false.  It is rather more like a fan spreading out from the one spot, the two branches a simplification of the fact.  If the fan was segregated by a physical barrier the segments of the fan would change subtly over time so that they would become separate species.  If they were not separated physically there might be inter breeding and then there would only be one species not two. The common ancestor of chimps and humans was also the common ancestor of all the near humans, about twelve species, the Bonobo Chimp and all the proto chimps that there may have been.  At this point there are Chimps, Bonobos and Humans, but the fork includes everything else, it is just not important as they are dead ends.