Revisiting Leigh Van Valen’s “A New Evolutionary Law” (1973) by Ricard Solé, (Biological Theory (2022) 17:120–125)
Now, here, you see, it takes all the running you can do, to keep in the same place.
Lewis Carroll, Through the Looking-Glass
Leigh Van Valen was an American evolutionary biologist who made major contributions to evolutionary theory. He is particularly remembered for his groundbreaking paper “A New Evolutionary Law” (1973) where he provided evidence from fossil record data that the probability of extinction within any group remains essentially constant through time.
In order to explain such an unexpected result, Van Valen formulated a very influential idea that he dubbed the RQH: “Red Queen hypothesis.” It states that the constant decay must be a consequence of evolutionary interactions among connected species within ecological networks.
In Van Valen’s picture, species do not merely evolve: they also coevolve with other species. As a consequence, when thinking about adaptation to an external environment, the other species must be considered as part (maybe a major part) of such an external world.
Van Valen’s law provided the first complex systems theory of coevolutionary dynamics and inspired a whole range of theoretical and experimental developments from very diverse fields, percolating far beyond its original formulation. Red Queen arms races are nowadays considered a widespread feature of complex adaptive systems.
Different levels of complexity involve new phenomena that cannot be reduced to the previous scale.
Here we show: a single species, b pairwise interactions, c ecological networks, and d evolving communities on a macro ecological timescale. Despite the dominant species-level picture of evolution grounded in gene frequencies, the addition of interactions (even pairwise) leads to novel phenomena. Each scale has been explored by means of a diverse range of mathematical models (e): from bottom to top, novel features are included such as species-species interactions, diversity, evolving interactions, or large-scale macroevolution. This increasing complexity inevitably leads to increasing unpredictability as network-level traits become dominant
His RQH was certainly a nonlinear, extraordinary insight. The key concept has been shown to be correct and central to our understanding of evolution. In many ways, Van Valen can be said to have been able to peer through the Looking Glass and foresee a whole land of open-ended possibilities.
The Red Queen has inspired further evolutionary metaphors, including
(a) the Red King dynamics of mutualistic communities, where the slowly evolving species is likely to gain a disproportionate share of the benefits (instead of the faster changing one),
(b) the Black Queen hypothesis, which proposes that gene loss can provide a selective advantage by conserving an organism’s limiting resources, and especially relevant for microbial communities
(c) the Suicide King, a phenomenon related to the maladaptive coevolution of parasites that can lead to the extinction of their hosts.
Of course,
Alice also met the White Queen, as already mentioned.
Surtil : 