How did darwin come across his theory of evolution?

"The Origin of Species" while extremely fascinating from a scientific and historical point of view is not an easy read - and definitely not something to try to wade through if your report is due soon.

Basically,during his travels about the world Darwin began to notice that animals were similar but not identical in various area. He collected lots of material everywhere as well as in the Galapagos. When he got back to England, he began to look at it. He also bred a lot of the breeds of domestic pigeon and studied their origins. People already had realized that animals change through time, but they didn't have a mechanism to explain why. Darwin realized that natural selection was responsible. Selection didn't have to be intelligent, it just HAD to be. It could be cold, it could be drought, it could be a predator eating certain colored young more than another color of young. It made no difference. So long as selection existed, it provided a mechanism for change.

Darwin had no idea WHAT changed. He had no knowledge of genetics. No knowledge of DNA, but he did know that animals produce young and that not all these young grow up to reproduce. Also, those that do reproduce have some that leave more viable young than do others.

BTW - Independently of Darwin another young man was noticing the same thing in a different part of the world. He sent a letter to Darwin detailing his findings and his hypothesis. It was so close to Darwin's findings that he might almost have read Darwin's notes. That young man was Alfred R. Wallace.

The story goes that when Darwin visited the Galapagos islands, he noticed that on each island there were finches (a small bird) and depending on the flora of each island, the finches had each developed adaptations to best exploit their respective islands. ie bigger beaks for breaking hard nuts etc. Since the plant life (food) on each island was slightly different, the birds adapted to the available food. Darwin assumed the island chain was at one point a single landmass that slowly pulled apart and at some point the islands were too far apart for the finches fly & thereafter the gene pool was isolated.

Upon returning from his voyage he did further research on domestic animals in secret. His theory wasn't published until on his deathbed.

Read the Origin of Species. Most of it came about when he visited the Galapagos Islands. Essentially he found several different specialized animals on the island and made some keen observations.

The idea of biological evolution had been around for thousands of years before Darwin. Darwin simply gathered the data to support it scientifically and proposed the mechanisms by which biological evolution occurs.

I agree with the answers b4 me, read the book "The Origin of Species" and u'll find out.

try reading the cliff notes for Origins of Species.