question: Why did most scientists accept the validity of evolution by the 1870s , but considered natural selection a minor part of it ?
answer: they believed evolution was purposeful and progressive .
turker_answer: Most scientists accepted the validity of evolution by the 1870s , but considered natural selection a minor part of it because they believed evolution was purposeful and progressive .
rule-based: Most scientists accepted the validity of evolution by the 1870s , but considered natural selection a minor part of it because they believed evolution was purposeful and progressive .