Paper short abstract:

Recent technological advances have revolutionised the study of DNA, allowing the analysis of ancient DNA and elusive epigenetic marks. These atypical molecular data provide new ways of measuring evolutionary times, and ultimately reveal that molecular time is all but relative.

Paper long abstract:

The study of the evolutionary and demographic history of our species, as well as other living organisms, depends heavily on the calibration of time. Whether it be calendar, isotopic, or molecular, time must be broken down into fundamental constant units to measure evolutionary changes. Recent technological advances have led to routine high-throughput DNA analyses in large cohorts of a wide range of living organisms, which in turn revealed that many different molecular clocks drive evolution. These DNA clocks can have different ticking frequencies depending on which biological parameter is measured (e.g. DNA sequences, epigenetic modifications, phenotypes). In addition, molecular clocks based on changes in the primary DNA sequence are themselves time-dependent, whereby the rate of observable changes in not constant depending on the depth of evolutionary time, natural selection, life history traits, or population demography. In this paper, I will present evolutionary lessons learnt from the study of ancient DNA—the study of DNA in sub-fossil biological specimens—and epigenetics. I will focus in particular on the time-dependency of DNA rates of evolution, as well as on the new perspective that epigenetics offers to understand rapid adaptation to changing environments.