RE: Need help with evolution
April 26, 2015 at 11:11 pm
(This post was last modified: April 26, 2015 at 11:30 pm by nihilistcat.)
(April 26, 2015 at 10:14 pm)nicanica123 Wrote: Hello, I am trying to understand evolution better. I have been raised my whole life as one of Jehovah's Witnesses. We believe the earth is billions of years old. We believe that animals do evolve, but we do not believe in evolution in a macro way. Please help me in my quest to understand scientific consensus more soundly. I need links, articles, facts, or whatever that can help me to understand evolution better. And why I can trust the facts. Thanks
If you have specific questions, I'd be glad to offer my input (I'm a biologist).
As I'm sure you're aware, we have millions of pieces of fossil evidence, spanning back over 3 billion years, including the skeletal remains of at least 14 or 15 different species of hominid (our direct ancestors).
But the questions I usually get from non-scientists tend to center on ... how precisely does a species evolve over time?
The simple answer is, mutations in our genome. Mutations occur constantly. Each time our cells divide, there's a small number of mutations (even though we have very good DNA repair mechanisms, they're not perfect, and so mutations happen somewhat randomly in most cases).
In some rare instances, these mutations become heritable. In some cases, these mutations can actually cause a physical alteration in the organism. For instance, a mutation created light skin complexion, which conferred a selective advantage (improved chances of survival) in cold climates. Lighter skin is less prone to frost bite. Moreover, in darker skinned people, eumelonin is prevalent, which acts as a natural sunscreen, while in lighter skinned people, pheomelanin (which produces vitamin D more efficiently) is prevalent.
This very minor variation produced an immense selective advantage when it comes to survivability in cold, northern climates; and the colder the climate, the more of an advantage fair skin produced. Since those with fairer skin (in cold climates) were more likely to survive, they were of course also more likely to reproduce and pass their genes to the next generation.
After several generations, eventually the genotype that produces a phenotype (physical characteristic) which confers a selective advantage, dominates over other genotypes.
Another big point of confusion I often run into concerns the cambrian explosion. However, it's thought that the appearance of the ozone layer (which appeared around the time of the cambrian explosion) and increases in atmospheric oxygen, allowed for an increase in diversity and complexity among eukaryotes. Another factor was an increase in calcium levels (caused by volcanic activity), which allowed marine organisms to build skeletons and hard body parts (and horizontal gene transfer was another possible contributor).
Okay, small example of how evolution works ... again, feel free to ask questions.
