Research shows that Darwin and Wallace are both right about the evolution of butterflies

Groundbreaking AI research on butterflies has explored the understudied evolution of females and adds to the debate among evolution’s founding fathers.

The University of Essex study, published in Communication Biology– examines a controversy between Victorian scientists Charles Darwin and Alfred Russel Wallace.

Darwin thought that men had more variety because women often chose their mates based on male appearance. While Wallace thought that natural selection between the sexes was the biggest factor in the difference.

For over a century, scientists have mainly studied men because their differences are more apparent, while women, with subtler evolutionary changes, have been less studied.

Using high-tech machine learning, Dr. Jennifer Hoyal Cuthill more than 16,000 male and female birdwing butterflies, with collaborators from the Natural History Museum and AI research institute Cross Labs, Cross Compass. This is the first time that visual differences between the sexes have been examined in the species, which occur in Southeast Asia and Australasia.

Birdwing butterflies were chosen for this study because of their spectacular wing color patterns and the differences between males and females.

Dr. Cuthill from the School of Life Sciences said: “This is an exciting time, with machine learning enabling new, large-scale tests of long-standing questions in evolutionary science.

“For the first time, we can measure the apparent extent of evolution to test how much variation exists across different biological groups and among both males and females. Machine learning is giving us new information about the evolutionary processes that generate and maintain biodiversity, including in historically neglected groups.”

The study looked at photographs of butterflies from the Natural History Museum’s collections, which show a range of features, such as wing shapes, colours and patterns, across different species. It found that while males tend to have more distinctive shapes and patterns, both males and females contribute to the overall diversity.

The research showed that evolutionary patterns predicted by both Darwin and Wallace were found in the butterflies, showing that both males and females contribute to the diversity between species. The males showed more variation in appearance, which fits with Darwin’s idea that females choose mates based on these traits.

However, in-depth research also revealed that there was subtle variation in females, consistent with Wallace’s predictions about natural selection allowing diversity in female phenotypes.

Dr Cuthill said: “Birdwings are described as some of the most beautiful butterflies in the world and this study gives us new insights into the evolution of their remarkable but threatened diversity.

“In this case study of birdwing butterfly photographs, sex appears to have driven the greatest evolutionary change, including extreme male morphs, colors, and patterns. However, within the birdwing moth group, we found contrasting examples where female birdwing moths are more diverse in visible phenotype than males, and vice versa.

“High visible diversity among male butterflies supports the real importance of sexual selection, from female mate choice to male variation, as originally suggested by Darwin. Cases in which female butterflies are visibly more diverse than the males of their species support an additional, important role for naturally selected female variation in interspecies diversity, as proposed by Wallace.

“Large-scale evolutionary studies using machine learning offer new opportunities to resolve debates that have been open since the inception of evolutionary science.”