A few relevant references (I don't have access to
the full text on these - except the PNAS paper
which is freely available):
J Anat. 2008 Apr;212(4):337-53.
Links
Reconstructing phylogenies and phenotypes: a molecular view of human evolution.
Bradley BJ.
Department of Zoology and Christ's College,
University of Cambridge, UK. bjb37@cam.ac.uk
This review broadly summarizes how molecular
biology has contributed to our understanding of
human evolution. Molecular anthropology began in
the 1960s with immunological comparisons
indicating that African apes and humans were
closely related and, indeed, shared a common
ancestor as recently as 5 million years ago.
Although initially dismissed, this finding has
proven robust and numerous lines of molecular
evidence now firmly place the human-ape
divergence at 4-8 Ma. Resolving the trichotomy
among humans, chimpanzees and gorillas took a few
more decades. Despite the readily apparent
physical similarities shared by African apes to
the exclusion of modern humans (body hair,
knuckle-walking, thin tooth enamel), the
molecular support for a human-chimpanzee clade is
now overwhelming. More recently, whole genome
sequencing and gene mapping have shifted the
focus of molecular anthropology from phylogenetic
analyses to phenotypic reconstruction and
functional genomics. We are starting to identify
the genetic basis of the morphological,
physiological and behavioural traits that
distinguish modern humans from apes and apes from
other primates. Most notably, recent comparative
genomic analyses strongly indicate that the
marked differences between modern humans and
chimpanzees are likely due more to changes in
gene regulation than to modifications of the
genes themselves, an idea first proposed over 30
years ago. Almost weekly, press releases describe
newly identified genes and regulatory elements
that seem to have undergone strong positive
selection along the human lineage. Loci involved
in speech (e.g. FOXP2), brain development (e.g.
ASPM), and skull musculature (e.g. MYH16) have
been of particular interest, but some surprising
candidate loci (e.g. those involved in auditory
capabilities) have emerged as well. Exciting new
research avenues, such as the Neanderthal Genome
Project, promise that molecular analyses will
continue to provide novel insights about our
evolution. Ultimately, however, these molecular
findings can only be understood in light of data
from field sites, morphology labs, and museum
collections. Indeed, molecular anthropology
depends on these sources for calibrating
molecular clocks and placing genetic data within
the context of key morphological and ecological
transitions in human evolution.
Heredity. 2008 Jun;100(6):555-63. Epub 2008 Mar 5.
Links
Genetic evidence and the modern human origins debate.
Relethford JH.
Department of Anthropology, State University of
New York College at Oneonta, Oneonta, NY 13820,
USA. relethjh@oneonta.edu
A continued debate in anthropology concerns the
evolutionary origin of 'anatomically modern
humans' (Homo sapiens sapiens). Different models
have been proposed to examine the related
questions of (1) where and when anatomically
modern humans first appeared and (2) the genetic
and evolutionary relationship between modern
humans and earlier human populations. Genetic
data have been increasingly used to address these
questions. Genetic data on living human
populations have been used to reconstruct the
evolutionary history of the human species by
considering how global patterns of human
variation could be produced given different
evolutionary scenarios. Of particular interest
are gene trees that reconstruct the time and
place of the most recent common ancestor of
humanity for a given haplotype and the analysis
of regional differences in genetic diversity.
Ancient DNA has also allowed a direct assessment
of genetic variation in European Neandertals.
Together with the fossil record, genetic data
provide insight into the origin of modern humans.
The evidence points to an African origin of
modern humans dating back to 200,000 years
followed by later expansions of moderns out of
Africa across the Old World. What is less clear
is what happened when these early modern humans
met preexisting 'archaic human' populations
outside of Africa. At present, it is difficult to
distinguish between a model of total genetic
replacement and a model that includes some degree
of genetic mixture.
Proc Natl Acad Sci U S A. 2008 Mar 4;105(9):3215-20. Epub 2008 Feb 27.
Links
Distinct genomic signatures of adaptation in pre-
and postnatal environments during human evolution.
Uddin M, Goodman M, Erez O, Romero R, Liu G,
Islam M, Opazo JC, Sherwood CC, Grossman LI,
Wildman DE.
Center for Molecular Medicine and Genetics and
Department of Anatomy and Cell Biology, Wayne
State University School of Medicine, Detroit, MI
48201, USA.
The human genome evolution project seeks to
reveal the genetic underpinnings of key
phenotypic features that are distinctive of
humans, such as a greatly enlarged cerebral
cortex, slow development, and long life spans.
This project has focused predominantly on
genotypic changes during the 6-million-year
descent from the last common ancestor (LCA) of
humans and chimpanzees. Here, we argue that
adaptive genotypic changes during earlier periods
of evolutionary history also helped shape the
distinctive human phenotype. Using comparative
genome sequence data from 10 vertebrate species,
we find a signature of human ancestry-specific
adaptive evolution in 1,240 genes during their
descent from the LCA with rodents. We also find
that the signature of adaptive evolution is
significantly different for highly expressed
genes in human fetal and adult-stage tissues.
Functional annotation clustering shows that on
the ape stem lineage, an especially evident
adaptively evolved biological pathway contains
genes that function in mitochondria, are
crucially involved in aerobic energy production,
and are highly expressed in two energy-demanding
tissues, heart and brain. Also, on this ape stem
lineage, there was adaptive evolution among genes
associated with human autoimmune and
aging-related diseases. During more recent human
descent, the adaptively evolving, highly
expressed genes in fetal brain are involved in
mediating neuronal connectivity. Comparing
adaptively evolving genes from pre- and
postnatal-stage tissues suggests that different
selective pressures act on the development vs.
the maintenance of the human phenotype.
Curr Biol. 2007 Nov 6;17(21):1908-12. Epub 2007 Oct 18.
Links
Comment in:
Curr Biol. 2007 Nov 6;17(21):R917-9.
The derived FOXP2 variant of modern humans was shared with Neandertals.
Krause J, Lalueza-Fox C, Orlando L, Enard W,
Green RE, Burbano HA, Hublin JJ, Hänni C, Fortea
J, de la Rasilla M, Bertranpetit J, Rosas A,
Pääbo S.
Max Planck Institute for Evolutionary
Anthropology, Deutscher Platz 6, 04103 Leipzig,
Germany.
Although many animals communicate vocally, no
extant creature rivals modern humans in language
ability. Therefore, knowing when and under what
evolutionary pressures our capacity for language
evolved is of great interest. Here, we find that
our closest extinct relatives, the Neandertals,
share with modern humans two evolutionary changes
in FOXP2, a gene that has been implicated in the
development of speech and language. We
furthermore find that in Neandertals, these
changes lie on the common modern human haplotype,
which previously was shown to have been subject
to a selective sweep. These results suggest that
these genetic changes and the selective sweep
predate the common ancestor (which existed about
300,000-400,000 years ago) of modern human and
Neandertal populations. This is in contrast to
more recent age estimates of the selective sweep
based on extant human diversity data. Thus, these
results illustrate the usefulness of retrieving
direct genetic information from ancient remains
for understanding recent human evolution.
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Received on Thu Feb 26 14:34:57 2009
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