BIOE 109Summer 2009

Lecture 13- Part IIHuman evolution

Human evolution  

• humans are classified within the superfamily Hominoidea (with gibbons, orangutans, gorillas and chimpanzees).

Human evolution  

• humans are classified within the superfamily Hominoidea (with gibbons, orangutans, gorillas and chimpanzees).

Human evolution  

• humans are classified within the superfamily Hominoidea (with gibbons, orangutans, gorillas and chimpanzees).

Similarity between human and chimpanzee genomes

Comparison of the human and chimpanzee genomes

  

Comparison of the human and chimpanzee genomes

  

• the genome of “Clint” was published September 1, 2005. 

Comparison of the human and chimpanzee genomes

  

• the genome of “Clint” was published September 1, 2005. 

• mean nucleotide divergence between humans and chimps was 1.06%. 

Comparison of the human and chimpanzee genomes

  

• the genome of “Clint” was published September 1, 2005. 

• mean nucleotide divergence between humans and chimps was 1.06%.  

• differ by 1 chromosomal fusion (human chromo. 2) and at least 9 pericentric inversions.  

The evolution of human chromosome 2

Comparison of the human and chimpanzee genomes

  

• the genome of “Clint” was published September 1, 2005. 

• mean nucleotide divergence between humans and chimps was 1.06%.  

• differ by 1 chromosomal fusion (human chrom. 2) and at least 9 pericentric inversions.  

• 13,454 human and chimp genes with unambiguous homology were aligned. 

Comparison of the human and chimpanzee genomes

  

• the genome of “Clint” was published September 1, 2005. 

• mean nucleotide divergence between humans and chimps was 1.06%.  

• differ by 1 chromosomal fusion (human chrom. 2) and at least 9 pericentric inversions.  

• 13,454 human and chimp genes with unambiguous homology were aligned. 

• 29% of all proteins compared were identical!

The primate fossil record 

The primate fossil record 

• primates first appear in the late Cretaceous (about 70 MYA).

The primate fossil record 

• primates first appear in the late Cretaceous (about 70 MYA).

• the first anthropoid ape fossil dates to Algeria (50 MYA).

The primate fossil record 

• primates first appear in the late Cretaceous (about 70 MYA).

• the first anthropoid ape fossil dates to Algeria (50 MYA).

• small anthropoid apes found in Egypt (30 MYA) and Kenya (25 MYA).

The primate fossil record 

• primates first appear in the late Cretaceous (about 70 MYA).

• the first anthropoid ape fossil dates to Algeria (50 MYA).

• small anthropoid apes found in Egypt (30 MYA) and Kenya (25 MYA).

• another gap to 15 MYA when several small hominids roaming N. Africa.

The primate fossil record 

• primates first appear in the late Cretaceous (about 70 MYA).

• the first anthropoid ape fossil dates to Algeria (50 MYA).

• small anthropoid apes found in Egypt (30 MYA) and Kenya (25 MYA).

• another gap to 15 MYA when several small hominids roaming N. Africa.

• very few fossils from 6 to 14 MYA!

Evolution of Homo sapiens

These 3.6-million-year-old footprints from Laetoli, Tanzania were made

by a pair of individuals who walked side-by-side through fresh ash

from a volcanic eruption.

Time(MYA)

Evolution of Homo sapiens5

4

3

2

1

0

Ardipithecus ramidus (4.4 – 4.2 MYA) Australopithecus anamensis (4.2 – 3.9 MYA)

A. afarensis (“Lucy”, 3.9 – 3.0 MYA)

A. africanus (2.8 – 2.4 MYA)

Homo habilis (2.5 – 1.6 MYA)

H. ergaster (1.8 – 1.5 MYA)

H. erectus (1.2 – 0.4 MYA)

H. heidelbergensis (0.6 – 0.2 MYA)

H. sapiens (0.15 MYA)

Features of early hominid evolution   

Features of early hominid evolution   

1. Exact path of descent unknown

 

Features of early hominid evolution   

1. Exact path of descent unknown

• more hominid species continue to be discovered.

 

Features of early hominid evolution   

1. Exact path of descent unknown

• more hominid species continue to be discovered.

 

Features of early hominid evolution   

1. Exact path of descent unknown

• more hominid species continue to be discovered.

2. Evolution was continuous and gradual

 

Features of early hominid evolution   

1. Exact path of descent unknown

• more hominid species continue to be discovered.

2. Evolution was continuous and gradual

• no sudden “jumps” in size or cranial capacity observed.

 

Features of early hominid evolution   

1. Exact path of descent unknown

• more hominid species continue to be discovered.

2. Evolution was continuous and gradual

• no sudden “jumps” in size or cranial capacity observed.

• cranial capacity increased from 600-800 cm3 to 1200-1400 cm3 over past 2 MY. 

Gradual evolution of human cranial capacity

Features of early hominid evolution   

3. Many hominid species co-existed in Africa

 

Features of early hominid evolution   

3. Many hominid species co-existed in Africa

• notably the “robust” Australopithecines.  

Diversity of fossil hominid species in Africa

Neanderthals – not in my family tree!  

Neanderthals!  

• Homo sapiens neanderthalensis lived in western Europe 400,000 to 30,000 years ago.

Neanderthals!  

• Homo sapiens neanderthalensis lived in western Europe 400,000 to 30,000 years ago.

• average height was about 5’4’’ but weighed about 20 lbs more than H. sapiens sapiens (due to extra muscle). 

Neanderthals!  

• Homo sapiens neanderthalensis lived in western Europe 400,000 to 30,000 years ago.

• average height was about 5’4’’ but weighed about 20 lbs more than H. sapiens sapiens (due to extra muscle).

• in 1997, Neanderthal mtDNA was amplified and sequenced (360 bp). 

Neanderthals!  

• Homo sapiens neanderthalensis lived in western Europe 400,000 to 30,000 years ago.

• average height was about 5’4’’ but weighed about 20 lbs more than H. sapiens sapiens (due to extra muscle).

• in 1997, Neanderthal mtDNA was amplified and sequenced (360 bp).

• recently, 1 million bp of Neanderthal DNA has been sequenced (and the full genome is on the way…). 

Conclusions: 

Conclusions: 1. Neanderthals diverged from the modern human

lineage ~600,000 – 800,00 years ago.

Conclusions: 1. Neanderthals diverged from the modern human

lineage ~600,000 – 800,00 years ago.

2. Little evidence of any introgression of Neanderthal DNA into modern humans.

 

Conclusions: 1. Neanderthals diverged from the modern human

lineage ~600,000 – 800,00 years ago.

2. Little evidence of any introgression of Neanderthal DNA into modern humans.

 3. Effective population size ~3,000 (compared to

13,000 for early modern humans).

…….. The last refuge

The evolution of anatomically modern humans

The evolution of anatomically modern humans

The evolution of anatomically modern humans

Predictions of the African Replacement model

 

Predictions of the African Replacement model

 

1. Ancestral alleles should trace to Africa. 

Predictions of the African Replacement model

 

1. Ancestral alleles should trace to Africa. 2. Appearance of modern humans should be recent (< 200,000 years).

Predictions of the African Replacement model

 

1. Ancestral alleles should trace to Africa. 2. Appearance of modern humans should be recent (< 200,000 years).

3. Genetic diversity should be greatest in Africa.

Predictions of the African Replacement model

 

1. Ancestral alleles should trace to Africa. 2. Appearance of modern humans should be recent (< 200,000 years).

3. Genetic diversity should be greatest in Africa.

• all three predictions have been confirmed.

Predictions of the African Replacement model

 

1. Ancestral alleles should trace to Africa. 2. Appearance of modern humans should be recent (< 200,000 years).

3. Genetic diversity should be greatest in Africa.

• all three predictions have been confirmed.

•“mitochondrial Eve” and “Y-chromosome Adam” lived in Africa about 150,000 and 60,000 years ago, respectively!

Complete mtDNA genomes from 53 humans

Recent evidence refuting the African replacement hypothesis

Recent evidence refuting the African replacement hypothesis

• in 2005 Alan Templeton reconstructed the history of human populations by analyzing 25 gene trees.

Recent evidence refuting the African replacement hypothesis

• in 2005 Alan Templeton reconstructed the history of human populations by analyzing 25 gene trees.

• his analysis rejects the complete replacement hypothesis with a probability equal to 10-17!

Recent evidence refuting the African replacement hypothesis

• in 2005 Alan Templeton reconstructed the history of human populations by analyzing 25 gene trees.

• his analysis rejects the complete replacement hypothesis with a probability equal to 10-17!

• he detected three waves of migration out of Africa.

“Out of Africa again and again”

Based on genetic markers

Conclusions

1. Evolution is the foundation of all biology!

Conclusions

1. Evolution is the foundation of all biology!

2. Evolution is relevant!

Conclusions

1. Evolution is the foundation of all biology!

2. Evolution is relevant!

• in health and medicine…

Conclusions

1. Evolution is the foundation of all biology!

2. Evolution is relevant!

• in health and medicine…

• in agriculture and natural resources…

Conclusions

1. Evolution is the foundation of all biology!

2. Evolution is relevant!

• in health and medicine…

• in agriculture and natural resources…

• in environmental and conservation issues…

Conclusions

1. Evolution is the foundation of all biology!

2. Evolution is relevant!

• in health and medicine…

• in agriculture and natural resources…

• in environmental and conservation issues…

• in understanding nature and humanity…

Conclusions

3. Natural selection rules!

Conclusions

3. Natural selection rules!

… but can’t do it all.

Conclusions

3. Natural selection rules!

… but can’t do it all.

• can’t simultaneously maximize all components of fitness…

Conclusions

3. Natural selection rules!

… but can’t do it all.

• can’t simultaneously maximize all components of fitness…

• can’t control neutral evolution…

Conclusions

3. Natural selection rules!

… but can’t do it all.

• can’t simultaneously maximize all components of fitness…

• can’t control neutral evolution…

• can’t direct adaptive evolution in small populations…

Conclusions

3. Natural selection rules!

… but can’t do it all.

• can’t simultaneously maximize all components of fitness…

• can’t control neutral evolution…

• can’t direct adaptive evolution in small populations…

• can’t stop aging and death…()

Objectives for the course  

  

Objectives for the course  

1. To foster an approach that may be called “evolutionary” or “population” thinking.   

Objectives for the course  

1. To foster an approach that may be called “evolutionary” or “population” thinking. 

• distinguishes between “proximate” and “ultimate” questions.  

 

Objectives for the course  

1. To foster an approach that may be called “evolutionary” or “population” thinking. 

• distinguishes between “proximate” and “ultimate” questions. • focuses on the importance of genetic variation in natural populations.  

Objectives for the course

2. To foster an understanding of organisms in the context of their evolutionary histories.

Objectives for the course

2. To foster an understanding of organisms in the context of their evolutionary histories.

• necessitates an expansion of perspective to include deep time scales.

Objectives for the course

2. To foster an understanding of organisms in the context of their evolutionary histories.

• necessitates an expansion of perspective to include deep time scales.

• most characters are “inherited” from ancestral species.

Objectives for the course

3. To realize the potential and limits of evolutionary change within species.

Objectives for the course

3. To realize the potential and limits of evolutionary change within species.

• evolution is a “tinkerer” not an engineer.

Objectives for the course

3. To realize the potential and limits of evolutionary change within species.

• evolution is a “tinkerer” not an engineer.

4. To dispel any preconceived idea that evolution has any ultimate goal in mind.

The final exam 

The final exam

• Time: 6pm- 8pm (2 hours)• Cover lectures 8 (The adaptationist program) through 13 (Human evolution).

Part 1. Multiple choice. 20 questions, 2 points each, 40 points total.

Part 2. Distinctions. Answer 5 out of 6, 4 points each, 20 points total

Part 3. Short answers. 8-10 questions, 2-5 points each, 40 points total.

EXTRA Credit questions!!