The Elements of Evolution (43-15-4) Red Queen Hypothesis

 Red Queen Hypothesis

Now, here, you see, it takes all the running you can do, to keep in the same place. ~ the Red Queen in Lewis Carroll’s novel Through the Looking-Glass (1871), explaining to Alice in Wonderland why she is exhausted from running, yet finds herself still under the tree where she started

In 1973, American evolutionary biologists Leigh Van Valen and Michael Rosenzweig independently concluded that organisms must constantly adapt to merely survive. Van Valen termed his hypothesis “Red Queen”; Rosenzweig called it a “Rat Race.” In the annals of popular science, Van Valen won, thanks to the charming literary allusion.

In Van Valen’s view of Nature, species continually evolve, but their fitness never increases because each adaptation is countered by adaptations by their competitors and enemies.
~ English evolutionary biologist Michael Brockhurst

Animal studies have shown statistically constant extinction rates between competing species that coevolve. From this, Van Valen proposed the Red Queen hypothesis to explain his hypothesized law of constant extinction: that the probability of population extinction remains constant.

Leigh Van Valen formulated the law of constant extinction after attempting to show that the probability of extinction increases with taxon age and finding instead that it does not. ~ Finnish evolutionary biologist Indre Zliobaite et al

Other evolutionary biologists have invoked the Red Queen hypothesis to explain the advantage of sexual reproduction, in offering variability and faster adaptive response compared to more economical and efficient asexual reproduction. The Red Queen hypothesis has also been applied to host-parasite coevolution, and to explain aging as evolutionarily advantageous.

From the time a species originates to its demise, its evolutionary success may be measured in several ways, such as the extent of its geographical range. Such metrics often form a bell curve, with a rise toward a central peak, followed by a decline to extinction. This pattern has been repeatedly observed. 2 primary drivers are involved: biotic competition and abiotic environmental factors.

Evolutionary innovation is influenced by intrinsic factors – the less-predictable origin of the ‘right’ variants at the right time, able to exploit either existing or new resources. ~ American paleobiologist Charles Marshall

Neither competition nor environmental change correlates well with the rates at which species arise. But, once expansion starts, the rate at which genera reach their peak in the fossil record strongly correlates with biotic competition intensity. The rise of large mammals was suppressed by dominant dinosaurs, for instance.

The probability of when a genus might reach its evolutionary peak is not related to how long it has been around. But, for large mammal herbivores at least, demise violates the law of constant extinction: the probability of extinction rises over time. (One known exception: the North American mammalian fossil record from the Cenozoic era fits the law of constant extinction with remarkable fidelity.)

Biotic drivers of evolution pertain mainly to the peak of taxon expansion, whereas abiotic drivers mainly apply to taxon extinction. At the end of its history, when a taxon is already rare, its final extinction is more likely to be a consequence of environmental change. In this light, the law of constant extinction might be usefully reformulated as the law of constant peaking. ~ Indre Zliobaite et al

The population dynamics behind evolutionary peaking and extinction resemble a gyre obeying self-organized criticality.