At that time, evolutionary biology was in eclipse. Many scientists thought that Lord Kelvin’s arguments about the rate of the earth’s cooling proved Darwin wrong (Kelvin 1862). Others recognized that Darwin’s theory of transmission by gemmules was inconsistent with his theory of natural selection (Richards 1987). Natural selection was not re-incorporated into biology until its underpinnings in population genetics were developed in the early to middle years of the 20th century (Fisher 1930). Even then, those foundations emphasized muta- tions and genetic variations, not the shaping of complex adaptations by selection, a field that was only developed by evolutionary and behavioral ecologists in the 1970s and later. Those insights into trait evolution are.
