Evolution II.

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.