let's talk about evolution and giraffes... :: RunningForums.com

MechEngDropout wrote:

jrjo wrote:

All that agreement hinges on the environments of mammals being the same as insects or bacteria. There's a huge difference in applying theories on the microscopic and insect level to that of mammals, imho. I won't for a minute argue with you about bacteria, but the life of a giraffe is a whole different existence. For example, look at cheryl's list of bacteria and how fast the mutations that benefit the species happen there. Why doesn't that happen to mammals? Man has been loping alongside giraffes for thousands of years and they haven't changed. Shouldn't the 'improvement curve' of mutations continue? Why the standstill in recent centuries while bacterias only continue to mutate even faster? dunno

Bacteria are much simpler than mammals. I think the evolutionary effect of mutations is greatly reduced when you get to the really complex lifeforms. I'm sure there are a lot of mutations in humans, but they don't show up because it's a relatively small part. Let's say for the sake of example a mutation occurs in one of every 100 bacteria. That's one percent of the organisms will have the mutation. But in people, if one percent of your cells have a mutation that lets you withstand radiation, you won't be able to withstand radiation. But that one bacterium out of 100 will because it's a fully functional organism. For a mutation to have an extensive effect on a complex organism it would have to occur very early in life at the first few cell divisions.

I'm just going off of what seems logical to me - someone let me know if I'm incorrect.

You're mostly right actually...bacteria are single-celled organisms and are extremely prolific therefore mutations can be readily seen within a short period of time.
Concerning multicellular organisms such as humans, in order for them to acquire a mutation that is inheritable and is able to be passed down successively to the next generation, the genetic change has to occur during gamete formation (sperm and egg). Therefore the offspring that arises from the union will receive the new genetic trait in their makeup and may or may not, depending on whether the change is recessive or dominant, display the mutant phenotype. Note that the change is present in all the cells in the offspring since after fertilization, the cells that divide from the zygote are copies of one another (how they differentiate into the different tissues & organs of the body is a whole other complicated story on gene regulation).
Therefore your notion on a small percent of cells in the body having a mutation is incorrect concerning inheritable (germline) mutations (all cells will have the mutation...depending on the cell type, the mutation may be expressed visibly).
A mutation that occurs in cells other than the sex cells results in cancer.
The reason why mutations are sometimes not visible is because they are 'masked' by other dominant genes...hence they are recessive.

let's talk about evolution and giraffes...

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