Right through high school and college, and right through popular science mags and shows, ‘evolution’ - discussions of natural selection - is very oversimplified and described in a misleading way.
For example, I am just about fed up with someone trying to explain that, “Giraffes developed long necks in order to reach food sources that were higher up and more abundant…it was natures way of adapting.”
Or, “…fish developed eyes so that they could see, and this adaptation gave them a survival advantage”
Or, “…Bacteria have become immune to X because it is overused…and by using X, we are making bacteria resistant…”
My understanding has always been this: Generation after generation after generation after generation of giraffe produced giraffes with different neck lenghts…and over time, because valuable food sources were higher up, slightly more and more longer necked animals were surviving long enough to reproduce at a slightly better clip…and over time longer necked giraffes were more abundant…etc.etc. Nature didn’t ‘adapt’…if anything there was a failure to adapt, and a chance beneficiary (longer necked giraffes) hung around longer to reproduce more. Heck…longer necks might have nothing to do with the reason longer necked giraffes survived. Maybe longer necked girrafes had slighty bigger eyes and that was the quirky characteristc that allowed them to hang around and reproduce more often/longer.
Or, when it comes to bacteria my understanding is this: While anitbiotics can wipe out 99% of bacteria when you are infected, the 1% left behind are basically the products on evolution put of fast-forward. The reproduce and become the dominant bacteria. The bacteria didn’t ‘become resistant’ in as much as 99% of it failed to ‘adapt’…leaving a little 1% of the population to become chance beneiciaries.
Mutations as well are not adaptations, but chance occurences that may or may not be advantageous almost by chance.
And the FLU bug for example…it actually mutates frequently, which is beneficial because it keeps us from guessing completely about what mutation will lead to what type of vaccine.
Anyway, I’d appreciate feedback on my understanding (which hardly captures what evolution is all about), but it is only intended to question the basics at the front door - the very basics that no one explains very well…thus how can we expect people to appreciate the whole concept…
What you’ve got there is natural selection, and you’ve got a pretty good handle on it. It’s a crucial element of evolution. the only major element to add is genetic drift over time. If a particular species has a large range, including desert and jungle regions, over time some random individuals with a slight edge will have more success in the desert, while other random individuals may have a slight edge in the jungle. Add a few millions years and the species becomes two, who now have permanent adaptive differences and can no longer interbreed.
Philster, you are correct. Darwin regretted the term “Natural Selection” since it gave rise to misunderstandings of his theory. As you have pointed out, using the adaption in relation to evolution is also misleading.
Keep in mind, Philster, that Natural Selection is an entirely negative process, which you seem to have grasped. A species ‘adapts’ over time, really by default. Individuals don’t adapt; the species as a whole does.
The apparent contradiction you’ve described is the difference between Darwinian theory, which describes the negative process of the elimination of less-‘adapted’ individuals, and Lamarckian theory, which posits a positive adaptive force (usually the Hand of God).
You seem to have a good understanding of how natural selection works. One thing to note is that bacteria can aquire resistance through a process called horizontal evolution in which they acquire genes directly from other organisms. By transformation (one of the 3 methods of gene exchange) bacteria can actually acquire DNA directly from the environment having been released from another cell. Since bacteria often develop their resistance on plasmids (called resistance transfer factors, or RTFs) they can easily spread their resistance to any bacteria they exchange genetic information with. This allows bacteria to evolve much faster than the “normal” process of natural selection which uses random mutations. In effect, bacteria can “infect” other bacteria with their genes. That is the main reason bacterial resistance is such a difficult problem to deal with.
Well, there are a few other elements as well, such as the genetic drift mentioned. Rapidly growing populations of a species will gain diversity in their genome. While they are still free to interbreed across the entire population, the total genome complexity can grow very much larger than it can in a narrowly confined population of the same species. The isolation of one portion of a population will create a gradually diverging genome, as mutational differences accumulate. When the differences themselves preclude interbreeding, most biologists call one a new species.
Of course in some cases the differences which preclude interbreeding are behavioral, or geographic, or individually logistic for the creatures. There is a good bit of difference in the opinions of biologists as to exactly what constitutes a difference in species. Just this week it was shown that stick bugs tend to breed much more frequently with other stick bugs that feed on the same one of the two plant species upon which all of them feed. It is not clear if the difference among the bugs are the reason, or the availability of mates on the same plant are the reason. At some point, someone has to decide when this is two species of stick bug.
The “fitness” thing is a post hoc evaluation. The ones that had more descendants are “more fit.” Of course the others might have been wiped out by volcanic eruptions, or abducted by aliens. But they have no descendants, so they were less fit.
I agree with the above posters: the OP’s understanding of evolution is the same as mine, anyway.
But I can’t resist pointing out that the giraffe example gets even more interesting (a real evolutionary arms race!)
The confusion, I think, is due to the scale on which evolution is talked about and may be related to the idea that one ant is dumb, but an ant colony is pretty smart. Scientific American had an article in their March 2000 issue Swarm Smarts by Eric Bonabeau & Guy Theraulaz, based on their book (an attempt to understand the process by which many simple units become a complex unit, with a view to improving software design), which is
reviewed at http://jasss.soc.surrey.ac.uk/4/1/reviews/kluegl.html
I really doubt that any modern text would use this wording, specifically the “in order” part. That is pure Lamarckianism and probably wouldn’t be in a textbook. Evolution, however, is often incorrectly explained with a bent towards their being an intentional process involved rather than adaptation merely being an epiphenomena of natural selection.