Most recent answer: 08/16/2017
- Manojkumar (age 25)
I'm not sure I understand your question, so I'll address two possible meanings.
The DNA changes that cause evolutionary changes happen essentially at random. Most of them don't work, and tend to get thrown out because the organisms that have them don't reproduce as much. A few work well in the sense that they cause more survival and reproduction, and these remain around to see.
Perhaps you're asking about how DNA directs complex cell differentiation, leading to formation of structures like the hand. That's a question for biologists to try to answer.
(published on 08/16/2017)