Reconstruction of O. bamboli (Pavel Major / ICP) |
O. bamboli fossil (CC by Ghedoghedo) |
Reconstruction of O. bamboli (Pavel Major / ICP) |
O. bamboli fossil (CC by Ghedoghedo) |
Primate phylogenetic tree (from Wikipedia) with the aprox. placement of Archicebus |
Abstract
It was recently shown that rhythmic entrainment, long considered a
human-specific mechanism, can be demonstrated in a selected group of
bird species, and, somewhat surprisingly, not in more closely related
species such as nonhuman primates. This observation supports the vocal learning hypothesis
that suggests rhythmic entrainment to be a by-product of the vocal
learning mechanisms that are shared by several bird and mammal species,
including humans, but that are only weakly developed, or missing
entirely, in nonhuman primates. To test this hypothesis we measured
auditory event-related potentials (ERPs) in two rhesus monkeys (Macaca mulatta),
probing a well-documented component in humans, the mismatch negativity
(MMN) to study rhythmic expectation. We demonstrate for the first time
in rhesus monkeys that, in response to infrequent deviants in pitch that
were presented in a continuous sound stream using an oddball paradigm, a
comparable ERP component can be detected with negative deflections in
early latencies (Experiment 1). Subsequently we tested whether rhesus
monkeys can detect gaps (omissions at random positions in the sound
stream; Experiment 2) and, using more complex stimuli, also the beat
(omissions at the first position of a musical unit, i.e. the ‘downbeat’;
Experiment 3). In contrast to what has been shown in human adults and
newborns (using identical stimuli and experimental paradigm), the
results suggest that rhesus monkeys are not able to detect the beat in
music. These findings are in support of the hypothesis that beat induction
(the cognitive mechanism that supports the perception of a regular
pulse from a varying rhythm) is species-specific and absent in nonhuman
primates. In addition, the findings support the auditory timing dissociation hypothesis,
with rhesus monkeys being sensitive to rhythmic grouping (detecting the
start of a rhythmic group), but not to the induced beat (detecting a
regularity from a varying rhythm).
Laure Ségurel et al., The ABO blood group is a trans-species polymorphism in primates. PNAS 2012. Pay per view (6 months embargo) ··> LINK [doi: ]
Abstract
The ABO histo-blood group, the critical determinant of transfusion incompatibility, was the first genetic polymorphism discovered in humans. Remarkably, ABO antigens are also polymorphic in many other primates, with the same two amino acid changes responsible for A and B specificity in all species sequenced to date. Whether this recurrence of A and B antigens is the result of an ancient polymorphism maintained across species or due to numerous, more recent instances of convergent evolution has been debated for decades, with a current consensus in support of convergent evolution. We show instead that genetic variation data in humans and gibbons as well as in Old World monkeys are inconsistent with a model of convergent evolution and support the hypothesis of an ancient, multiallelic polymorphism of which some alleles are shared by descent among species. These results demonstrate that the A and B blood groups result from a trans-species polymorphism among distantly related species and has remained under balancing selection for tens of millions of years—to date, the only such example in hominoids and Old World monkeys outside of the major histocompatibility complex.
Update: a pre-print copy of the paper is available at arXiv.
Abstract
Estimation of divergence times is usually done using either the fossil record or sequence data from modern species. We provide an integrated analysis of palaeontological and molecular data to give estimates of primate divergence times that utilize both sources of information. The number of preserved primate species discovered in the fossil record, along with their geological age distribution, is combined with the number of extant primate species to provide initial estimates of the primate and anthropoid divergence times. This is done by using a stochastic forwards-modeling approach where speciation and fossil preservation and discovery are simulated forward in time. We use the posterior distribution from the fossil analysis as a prior distribution on node ages in a molecular analysis. Sequence data from two genomic regions (CFTR on human chromosome 7 and the CYP7A1 region on chromosome 8) from 15 primate species are used with the birth–death model implemented in mcmctree in PAML to infer the posterior distribution of the ages of 14 nodes in the primate tree. We find that these age estimates are older than previously reported dates for all but one of these nodes. To perform the inference, a new approximate Bayesian computation (ABC) algorithm is introduced, where the structure of the model can be exploited in an ABC-within-Gibbs algorithm to provide a more efficient analysis.
Toumaï |
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