Darwin thought life evolved like a tree growing, with a single common trunk opening out into a myriad of branches and twigs. But today, says Prof. Ford Doolittle of Dalhousie University, Nova Scotia, at the forefront of fundamental research in evolutionary biology for over four decades, it’s clear the situation is more complex.

“For bacteria it may be more appropriate to speak of the Web of Life, because there is rampant exchange of genes across species lines. This web-like evolution is a challenge to neo-Darwinism, and a source of controversy within the discipline and in the public arena.”

He sets out his ideas in conversation.

The images are from the work of the artist Gemma Anderson, ‘Adaptation of Doolittle diagram’, pencil and watercolour on paper, 2015.

”The famous diagram by Ford Doolittle (slightly updated to represent transfers between archaeal and bacterial lineages) is delimited by a black outline, representing cellular lineages. It shows the vertical and lateral processes of evolution at the origin of cellular diversity. Purple and yellow vines (corresponding to the vertical and lateral evolution of viral and plasmid lineages, respectively) complement and expand this classic drawing of the web of life. Red lines indicate gene externalization events between cellular organisms and mobile genetic elements. ”

You can watch this free event from here, through the YouTube link below, or if you’d like to join questions and discussion, you can also go to the Science Festival’s YouTube channel