In “ Nature” this week, the widely accepted view of evolution (the eponymous hypothesis) that suggests evolution occurs through a ‘gradual accumulation of small changes over time’ has been challenged on the back of a study of the evolutionary trees of thousands of species.
This new research from the University of Reading shows instead that ‘single rare evolutionary events’ are responsible for the creation of new species, so rather than gradual changes; they suggest that the new species are formed by a ‘jump’ in evolution.
The traditional theory where evolution is driven by a constant churn of sexual selection would mean that all of the species in a family or genus would be forming into a new species at the same rate.
However, the study, which applied four different models of speciation to over 100 groups from both the plant and animal kingdom suggested that the eponymous hypothesis only fitted the histories of 8% of the thousands of different species studied.
In contrast, nearly 80% of the same trees fitted the ‘single rare evolutionary event’ model. These events could include a shift in climate or the sudden emergence of a new mountain range.
Aware that his research could prove controversial, lead researcher at Reading, Mark Pagel said "It really goes against the grain because most of us have this Darwinian view of speciation," "What we're saying is that to think about natural selection as the cause of speciation is perhaps wrong."
Despite the unorthodox methods of analysis, using a largely computerised approach to analyse data from phylogenetic trees, Pagel hopes other researchers will accept it as it “will start to unravel some mysteries about speciation," he says.