I want to know the answer to the following question:
What did two biologists point out in 1964?
All the background I'm provided with is that "In 1964, the biologists Paul Ehrlich and Holm pointed out cases where two or more clines are distributed discordantly—for example, melanin is distributed in a decreasing pattern from the equator north and south; frequencies for the haplotype for beta-S hemoglobin, on the other hand, radiate out of specific geographical points in Africa.". Is that enough to answer the question?
Answer: yes