These are not really phrases that would be used by most biologists. Changes in the frequency of particular versions of genes -alleles - accumulate over time. Deciding when micro becomes macro is very subjective. Obviously when a population has changed sufficiently that they can no longer interbreed with the parent species then an important line has been crossed. That can be a subtle as the difference between Herring Gulls and Lesser Black-backed Gulls or as startling as the gap between chimps and humans. It's all the same mechanisms at play.
Aha, so there is no real micro and macro so to speak. Or if there were just to play the word game the macro isn't like one huge jump, it is millions of years of micros and isolation that allows them to continue down that path.
Yes. The key thing to remember is that nothing ever adapts to its environment. Rather a variety of genetic variation exists within a gene-pool. When changes happen in an environment in an isolated breeding group then some of those variations will confer a slight advantage. The frequency of that mutation will then become more common - or even ubiquitous - in that population.
Okay, so adaptation is an incorrect term then? The environmental pressures do impact changes, but only in that they allow the various mutations that exist already to flourish or fail? Those that flourish eventually win over through breeding and the failing mutations disappear or go latent?
I'm getting hung up on the notion that nothing adapts to the environment. In Prothero's book he mentioned some birds and an island where the food source changed to nuts. So then, the birds that had beaks that could break open the nuts for sustenance already existed on the island, it isn't like over time they developed, but they now had an advantage? I could swear that I've read about animals that adapted to different climates and such. So that was incorrect?
Just to clarify we and chimps both evolved from a common ancestor about 6 million years ago. Both lineages have been changing since then. The genetic difference is now about 1.5% but that means that our genome has only changed by about half that amount in that time.
Oh, so we didn't evolve from chimps. Right, that's linear and not accurate. As the tree branches grew on this tree of life there was a limb that was common to us, but the branches off of that limb were different, gradually so of course and over time.
Three things to sort out here. One is that a change of just a few percent in a genome is still an awful lot of changes. We have three billion base pairs in our genome. Most mutations happen in the non-coding region and has a neutral effect.
That cures my issue with such seemingly "small" changes affecting such great differences. They aren't so small after all. Makes sense.
The other thing is to think about the genome more like a chemical formula or a recipe than a blueprint. A small change in a blueprint results in a small change in the building. A tiny change in chemical formula can have a radical change in the end result - be that a chemical compound or a sponge cake.
This blew my mind. I was thinking more of the blueprint. A change in the blueprint still results in a building being formed. Maybe different in appearance slightly, but still a building. Chemistry is on a whole different level. Fascinating.
The third point I want to make is about selective pressure. Life has evolved over millions of years to fill every possible niche on the planet. Having refined their design by natural selection there just isn't a strong pressure on most species to change.
So then, in some ways, evolution does kind of end with us, barring some strong change in environment. Of course, if environment itself evolves over time, so will other things. However, the isolation factor is not as easy to find anymore so that kind of removes one factor that contributes to a mutation's survival.
That is also why we get so many genetic illnesses in old age. There is no evolutionary pressure to eradicate those from the gene-pool.
So these illnesses come out because we can no longer procreate? With men still being able to procreate and women not being able to after a certain age, are there higher percentages of genetic illnesses found in the female population? Or am I missing this point altogether?
I hope I'm getting this. Feel free to correct any incorrect assertions above. Man, I don't know why this is so hard for me to grasp. I've always been a very linear thinker and the cult really pushed me in that way. I went and looked at some tree of life images to help me see things more clearly in my mind, and that video above from jp kind of helped too.
Thanks for working with me on this. I am sincerely trying to grasp this and change my mind over from the way I was taught. At the same time I don't want to just say that I accept evolution without understanding it, otherwise I'm not much better than my old creationist self, just accepting things blindly because an authority said so. I like that there is visible evidence for this stuff.
Oh, and are we related to the plants too? If I have to throw them in the mix my brain my break, lol.