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Evolution II. Dating of fossils. Relative Absolute. Relative dating. Absolute dating. Radiometric dating. 1,0. decay product. Share of isotope. 0,5. isotope. 0. t. Half-life. time. P rinciple of radiometric dating. Mesozoic. K-T Border (66-65 mil.y.): mass extinction. - PowerPoint PPT Presentation
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Evolution II.Evolution II.
Dating of fossils
• Relative
• Absolute
Relative dating
Absolute dating• Radiometric dating
IsotopeHalf-live (years)
K40 1,3 .1012
Th232 14 .1012
U235 704 .106
C14 5 730
Principle of radiometric dating
0,5
1,0
0t
Sh
are
of
iso
top
e
time
isotope
decay product
Half-life
Mesozoic
PERIODTIME
(milions of years)
Triassic
190
Jurassic136
Cretaceous
66
K-T Border (66-65 mil.y.): mass extinction
Chixculub Crater (Mexiko)
Site of colision with an asteroide measuring 10-20 km across
KenozoicPERIOD
Time(mil.y.)
CHARAKTERISTIC
Tertiary
53 Occurence of Prosimii
35 Occurence of Anthropoidea
25 Occurence of Hominoidea
5 Occurence of Dryopithecus
1,8 Hominids (Australopithecus)
Quarternary
Pleistocene
0,01
Homo habilisHomo erectus
Homo sapiens neanderthalensis
Holocene
recent
Homo sapiens sapiens
Cladistics• A method of analyzing
the evolutionary
relationships between
groups to construct their
family tree. Phylogenetic
relationship between
organisms is derived from
the similarity of certain
characters.
• Result of cladistic
analysis – cladogram.
Cladogram
hair? milk? lay eggs? livebearing? placenta?
platypus
x x x
echidna
x x x
opossum
x x x
cat
x x x x
elephant
x x x x
Simple cladogram of mammals
A cladogram derived from the molecular data (DNA sequence)
Possible fylogenetic relationships of hominides I.
0
0,25
0,5
1
2
3
4
5
6
Time (milions of years)
Homo sapiens sapiens Homo „sapiens“
neanderthalensis
Homo erectus
Homo habilis
Australopithecusafarensis
Ardipithecus ramidus
Australopithecus. africanusHomo
heidelbergensis
Tertiary
Quarternary
Possible fylogenetic relationships of hominides II.
Kenyantropus
Australopithecus africanus
Australopithecus africanus
Skull of „Taung child“ – found in south Africa
Australopithecus afarensis
Autralopithecus afarensisskeleton„Lucy“
Footsteps of A.afarensis (Laetoli, Tanzania)
Australopithecus walked upright
(bipedal)
Australopithecus afarensis
Homo habilis
Homo erectus
the first hominide living outside Africa
Homo erectus
Homo erectus
Homo heidelbergensis
0
0,25
0,5
1
2
3
4
5
6
Time (milions of years)
Homo sapiens sapiens Homo „sapiens“
neanderthalensis
Homo erectus
Homo habilis
Australopithecusafarensis
Ardipithecus ramidus
Australopithecus. africanusHomo
heidelbergensis
Possible fylogenetic relationships of hominides
Homo neanderthalensis
Homo neanderthalensis
Homo neanderthalensis
Homo neanderthalensis
X
Homo sapiens
Modern Homo sapiens
Lascaux cave (France)
– paintings of wild horses and aurochs (17 000 years ago).
http://www.modernhumanorigins.com/
About the origin of Homo sapiens
• Monocentric models
– Homo sapiens evolved in one site (probably in
the Africa) – out-of-Africa theory
• Polycentric models (multiregional
evolution)
– Homo sapiens evolved independently in a few
different sites. Modern humans originated of
crossbreedind of these different strains.
Out-of-Africa Theory
Mitochondrial Eve• The rate of mutations in the mitochondrial
genome (mtDNA) is constant – roughly 1/1500-3000 years.
• Comparison of these mutations could explain differences on possible relationship between different human populations. Its also possible to estimate the time of evolutionary division of their ancestors.
• mtDNA studies showed that the modern humans (Homo sapiens sapiens) differed from other species of the genus Homo before some 150 – 200 thousands of years. Homo sapiens originated from a small group of females (or only one female) – such called „mitochondrial Eve“, which delivered to us her mitochondrial genes.
• „Eve“ lived probably in Africa. It supports the hypothesis, that the whole mankind originated from only one ancestor (i.e. „out-of-Africa theory).
What hapenned with Homo neanderthalensis?
Theories• Homo sapiens evolved from H. neanderthalensis• H. sapiens and H. neanderthalensis were
different species, but H.neanderthalensis failed in competition with H. sapiens – (H.n. was a trophy of H.sapiens)
• There was numerous crossbreeding between H. sapiens and H. neanderthalensis. Current human population consist of descendants of the both of species.
Results of the mtDNA studies?
• Hypervariable sequences HVR I a HVR II of the mtDNA (aDNA) isolated from the fossil materials were analyzed.
• Intraspecific variability within the population of the modern humans reaches maximum only 11pb.
• Differences in HVR squences between the modern human and H. neanderthalensis are 35 pb. It could be explained as a interspecific difference.
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