Transcript Adam-geneticsx

Adam & Eve & Genetics
History of life on earth
If the earth was 24 hours old,
• then animals didn’t appear until the last 2
hours
• dinosaurs went extinct in the the last 20
minutes –
• anatomically modern humans -- the last
one or two seconds
• recorded history, about last 0.1s
• your lifespan, the last millisecond
Common descent in biology?
Page from Darwin's notebooks ~ circa1837 showing his first known sketch of an
evolutionary tree depicting common descent.
Case study 2: evolution of horses
homologies
Can sound like weak
inductive reasoning to
many physical scientists
Case study 3: common descent of human & chimp?
Divergence of the chimpanzee and human lineages occurred about 6 million years ago; the times of lineage divergence are not to scale
News & Views: The chimpanzee and us, Wen-Hsiung Li and Matthew A. Saunders, Nature 437, 50-51 (1September 2005) .
tapestry arguments in biology:
chromosomal banding:
Humans have 46 (2 X 23)
chromosomes
Apes have 48 (2 X 24)
chromosomes
chromosome 2: Human, Chimp, Gorilla, Orang-utan
The origin of man: a chromosomal pictorial legacy. J.J Yunis and O. Prakash, Science 215,
1525 (1982)
tapestry arguments in biology: fusion of
chromosome 2?
chromosome 2: Human, Chimp, Gorilla, Orang-utan
tapestry arguments in biology: evidence
from the human genome
Chromosome 2 is unique to the human lineage of evolution, having
emerged as a result of head-to-head fusion of two acrocentric
chromosomes that remained separate in other primates. The
precise fusion site has been located in 2q13−2q14.1 (ref. 2;
hg16:114,455,823−114,455,838), where our analysis confirmed the
presence of multiple subtelomeric duplications to chromosomes 1,
5, 8, 9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary Fig. 3a, region
A). During the formation of human chromosome 2, one of the two
centromeres became inactivated (2q21, which corresponds to the
centromere from chimp chromosome 13) and the centromeric
structure quickly deterioriated [42].
Generation and annotation of the DNA sequences of human
chromosomes 2 and 4, L.W. Hillier et al., Nature 434, 724 (2005).
endogenous retroviruses
HERV-K insertions
In humans endogenous retrovirus sequences make up about 1% of the genome.
Lebedev, Y. B., et al. (2000) "Differences in HERV-K LTR insertions in orthologous loci of humans and great
apes." Gene 247: 265-277.
tapestry arguments in biology: more
threads of evidence
•Genetic threads
•SINEs (Alu )
•LINEs
•Retroviral insertions
•pseudo genes (e.g. olefaction)
•chromosomal inversions
•Phenotypal similarities
•Fossils
Human brain size & out of Africa
Mitochondrial eve (150,000 -200,000 years)
Y-Chromosome Adam (50,00-80,000 years)
Not the only individual
Population size with time
Heng Li & Richard Durbin Nature 475, 493–496 (13 July 2011)
PSMC estimate on data simulated by msHOT. The blue curve is the population-size history
used in simulation; the red curve is the PSMC estimate on the originally simulated sequence;
the 100 thin green curves are the PSMC estimates on 100 sequences randomly resampled
from the original sequence. b, PSMC estimate on data with a variable mutation rate or with
hotspots. g, generation time; μ, mutation rate.