Sex chromosomes complex history in primates

Just a quick mention of what seems to be an important piece of research in the evolution of sex chromosomes in humans and primates in general. The main finding being the existence of a number of evolutionary gene conversions (transference between the X and Y chromosomes, in either direction).

Mineyo Iwase et al. Frequent gene conversion events between the X and Y homologous chromosomal regions in primates. BMC Evolutionary Biology 2010. doi:10.1186/1471-2148-10-225. Open access.


Conclusion

Gene conversion events between the X and Y homologous regions have been suggested, mainly in humans. Here, we found frequent gene conversions in the evolutionary course of primates. An insertion of a LINE element at the proximal end of the region may be a cause for these frequent conversions. This gene conversion in humans may also be one of the genetic causes of Kallmann syndrome.

Molecular clock speculation obscuring the real Jurassic origin of primates

Again reality and reason clash frontally with the molecular clock hypothesis (or at least the most common interpretations of it).

If we'd have to follow the molecular clock speculations, so fashionable these days, we'd have to have sailor monkeys, which would have crossed oceans to get into America already in the Eocene, when the Atlantic Ocean was already huge. Such a colossal feat is plainly impossible, even for humans before just some centuries ago, but the fanatics of the molecular clock religion have argued for transoceanic rafting and hypothetical "island hopping" en masse.

Non-human primate range.

Common Sense shakes its head in disbelief, Folly laughs delighted at the naivety of even some of the supposedly most brilliant human minds.

Luckily Reason still has good cards to play in this surrealistic meta-game of honest facts versus trickster blind faith. The card that Reason plays now reads:

Michael Heads, Evolution and biogeography of primates: a new model based on molecular phylogenetics, vicariance and plate tectonics. Zoologica Scripta 2010.

Abstract:

The ages of the oldest fossils suggest an origin for primates in the Paleocene (∼56 Ma). Fossil-calibrated molecular clock dates give Cretaceous dates (∼80–116 Ma). Both these estimates are minimum dates although they are often 'transmogrified' and treated as maximum or absolute dates. Oldest fossils can underestimate ages by tens of millions of years and instead of calibrating the time-course of evolution with a scanty fossil record, the geographical boundaries of the main molecular clades of primates are calibrated here with radiometrically dated tectonic events. This indicates that primates originated when a globally widespread ancestor (early Archonta) differentiated into a northern group (Plesiadapiformes, extinct), a southern group (Primates), and two south-east Asian groups (Dermoptera and Scandentia). The division occurred with the breakup of Pangea in the Early Jurassic and the opening of the central Atlantic (∼185 Ma). Within primates, the strepsirrhines and haplorhines diverged with volcanism and buckling on the Lebombo Monocline, a volcanic rifted margin in south-east Africa (Early Jurassic, ∼180 Ma). Within strepsirrhines, lorises and galagos (Africa and Asia) and lemurs (Madagascar) diverged with the formation of the Mozambique Channel (Middle Jurassic, ∼160 Ma). Within haplorhines, Old World monkeys and New World monkeys diverged with the opening of the Atlantic (Early Cretaceous, ∼130 Ma). The main aspects of primate distribution are interpreted as the result of plate tectonics, phylogeny and vicariance, with some subsequent range expansion leading to secondary overlap. Long-distance, trans-oceanic dispersal events are not necessary. The primate ancestral complex was already widespread globally when sea-floor spreading, strike-slip rifting and orogeny fractured and deformed distributions through the Jurassic and Cretaceous, leading to the origin of the modern clades. The model suggests that the topology of the phylogenetic tree reflects a sequence of differentiation in a widespread ancestor rather than a series of dispersal events.

The paper is behind paywall but you can read a synthesis at Science Daily.

The molecular clock, if it still makes any sense at all, is certainly much slower. Primates migrated to South America in the Jurassic, when it was still part of Gondwanaland.