Looking Back In Time

Jumping Bristletail

Jumping Bristletail, a Microcoryphian

Our understanding of life on earth is enhanced by the many efforts at historical reconstruction. These efforts are imprecise and subject to revision. New tools allow greater precision in our estimates. The oldest fossil insect wings date to about 324 million years ago (mya). These wing fossils are fully developed and sophisticated. Insect flight must have originated sometime earlier but how much earlier?

Modern DNA sequencing is used by modern biologists to reconstruct and date the insect family tree. The process of evolution, “descent with modification”, leaves a record of those “modifications” in the gene sequences of the descendants. Genes accumulate mutations (changes in DNA) over time at a reasonably predictable rate. Molecular phylogeny involves the study of these changes. Data analysis is by sophisticated computer algorithms. In a molecular phylogenetic study, scientists* sequenced 1478 genes from over 100 species and used information on those 1478 genes from previously published genomes. From the over 200,000 sequence, they used computer algorithms to generate a phylogenetic tree with approximate dates attached.

They date the first “insects” to around 479 mya, about the same time that plants first colonized land. This is 65 my earlier than the first insect fossils. They place the date of the first insect flight at around 406 mya. This adds to previous data to place evolution of flight over 400 mya. They suggest a split of Dragonflies and Mayflies (the uncertainty is large) from a common winged ancestor. This finding if further supported is inconsistent with the origin of flight in the mayflies and consistent with the origin of flight in a Thysanura (Silverfish)-like ancestor.

This study is not the final answer. But it does provide a framework for future studies and identifies a number of questions that could be resolved by more data. At this time of year, we reflect on the past to help guide our future.
Happy New Year

*Phylogenomics resolves the timing and pattern of insect evolution. Misof & Colleagues. Science. 7 November 2014: Vol.346, No.6210 pp. 763-767.
DOI: 10.1126/science.1257570

About jjneal

Jonathan Neal is an Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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