lineages with contrasting reproductive strategies remains poorly understood.” One would think that something of this magnitude would be well studied by now. Yet, it is not like we have no information on the topic. Indeed, much work has been done both on the short-term mutation rate and the variability in mutation rates. Genealogical studies have consistently produced rates much faster than phylogenetic studies. Hardouin and Tautz (2013) determined that the measurable fixation rate both in mice that had colonized the remote Kerguelen Archipelago and in lab-cultured mouse strains is about six times higher than that of phylogenetic estimates. Madrigal et al. (2009) measured a mitochondrial mutation rate of approximately 0.5 per generation in deep-rooting family trees. They also summarized prior studies, which claimed mutation rates ranging from 0.12 to 1.2 per generation (excluding the one study that discovered zero mutations among 292 generational steps). More recently, Connell et al. (2022) published the genealogical rate for 225 individuals from Norfolk Island spanning 345 generational events. Even though their estimate equated to only 0.029 mutations per generation, they claim this was 16 times higher than typical phylogenetic estimates. Since only a few dozen mutations separate most human mitochondrial groups, with a maximum separation of only a hundred or so (Carter et al. 2008), a mitochondrial mutation rate on the order of 0.5 per generation (Madrigal et al. 2012) would place Mitochondrial Eve in the recent past. Assuming an average generation time of about 30 years (Helgason et al. 2003), biblically, if humans have been around for ~6,000 years (Hardy and Carter 2014), only about 200 generations have occurred in human history. The number of mutations seen is approximately what would be expected (e.g., 200 generations x 0.5 mutations/generation = 100 mutations). That, of course, is a very rough estimate. On the other hand, there is no reason to expect mutation rates to Figure 1. The Y-chromosome family tree according to the Human Genome Diversity Panel (After Ding et al. 2021). The dotted line represents the average divergence from the (presumed, evolutionary) common ancestor of all living males. Since the number of mutations is proportional to branch length, clearly the men from several groups are well above average in the number of mutations they carry (e.g., A and B). One can even see differences in average branch length within the major groups (e.g., D and C). The mutation rate has not been constant across time and geography. CARTER Genealogical vs. phylogenetic mutation rates 2023 ICC 169
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