Eggs come in all sizes and shapes, depending on the species. Cassandra Extavour wants to understand why.
The professor of Organismic & Evolutionary biology and of Molecular & Cellular Biology at Harvard University has been fascinated by animal development since she was an undergraduate. In particular, Extavour has made major breakthroughs in the understanding of embryos and germ cells (eggs and sperm). But for many years, she was slightly isolated in her pursuit. Traditionally when biologists try to understand the evolution of egg cells, they have focused on a small subset of animals.
“If you count up all the different numbers of animal species, well over 80 percent of them are insects,” says Extavour. “However you want to measure it — number of species, number of organisms, bio mass on the Earth — it’s arthropods.”
Extavour decided it was time to systematically examine some of the major theories of ‘animal’ egg cells development. She and her team of graduate students Samuel H. Church, Seth Donoughe, and Bruno A.S. de Medeiros created software to find and digitize more than 3,000 papers from the last 300 years. With these 10,000 measurements they were able to test previously unverified hypotheses of egg size, shape, and evolution.
“We asked whether or not some of these popular hypotheses held up if we looked at the data. And the quick answer is a lot of them didn’t,” says Extavour.
Now with this database, Extavour and others can figure out principles which explain the evolution of animal eggs.
“Professor Extavour is absolutely relentless in her pursuit of evidence,” says BN Queenan, Executive Director of Research at Harvard’s NSF-Simons Center for Quantitative Biology. “She doesn’t care at all what people say, or believe. The conventional wisdom is completely irrelevant to her. She is trying to figure out the foundational principles of embryonic development and she’s not going to let someone’s untested theory get in her way.”
Nature article: https://www.nature.com/articles/s41586-019-1302-4
More on professor and professional soprano Extavour: https://www.nature.com/articles/d41586-019-02040-6