Abstract

There is a longstanding interest in whether the loss of complex characters is reversible (so-called "Dollos law"). Reevolution has been suggested for numerous traits but among the first was Kurten (1963), who proposed that the presence of the second lower molar (M2) of the Eurasian lynx (Lynx lynx) was a violation of Dollos law because all other Felids lack M2. While an early and often cited example for the reevolution of a complex trait, Kurten (1963) and Werdelin (1987) used an ad hoc parsimony argument to support their proposition that M2 reevolved in Eurasian lynx. Here I revisit the evidence that M2 reevolved in Eurasian lynx using explicit parsimony and maximum likelihood models of character evolution and find strong evidence that Kurten (1963) and Werdelin (1987) were correct - M2 reevolved in Eurasian lynx. Next, I explore the developmental mechanisms which may explain this violation of Dollos law and suggest that the reevolution of lost complex traits may arise from the reevolution of cis-regulatory elements and protein-protein interactions, which have a longer half-life after silencing that protein coding genes. Finally, I present a model developmental model to explain the reevolution M2 in Eurasian lynx.