> ... chemistry is extremely conservative all the way back to the first eukaryotes. Once our kind of life figures out a way to do something it's very uncommon t

> ... chemistry is extremely conservative all the way back to the first eukaryotes. Once our kind of life figures out a way to do something it's very uncommon that the fundamental pathways change Why don't most effects cross species barriers? Plenty of viruses, for example, affect some species but not others. When developing medical treatments, I thought that researchers had to carefully choose animal species analogs to humans for testing, and even then it was very unreliable.