His work charted the evolution from the early fishes through the various branches to birds and mammals, with numerous papers and two major works: Our Face from Fish to Man in 1929 and Evolution Emerging in 1951.
Realizou importantes traballos sobre a evolución desde os primitivos peixes até as distintas ramas de aves e mamíferos, publicando numerosos artigos e dúas grandes obras: Our Face from Fish to Man (1929) e Evolution Emerging (1951).