Population Genetics Flashcards
When did the hominid separate from apes?
7 million years ago - separated from apes
Why are our chromosomes different to those of apes?
There are inversions, translations and as humans we have many more function genes
How many chromosomes do chimpanzees have?
48 (we have 46)
Why have apes declined even more?
Hunting and disease (Ebola)
When did the bipedal hominids become apparent?
6 million years ago - had small canines
What are the main differences between hominins and apes?
- We have a greater dependence on adults during childhood
- We also have a longer life after menopause
- Humans have reduced diversity in some parts of the genome (part of X chromosome and mtDNA)
Where have examples of early hominins been found?
Chad, Kenya, Ethiopia
What was present in 4 million BCE?
Australopithecus
What were the four different hominid lineages that co-existed around 2 -1 million BCE?
Australopithecus
Homo Neanderthalensi
Homo floresiensis
Homo habilis
What type of ancestor was Lucy the fossil skeleton?
Australopithecus - unclear whether Lucy is a direct ancestor to the homo species
What were the characteristics of homo florensiensis?
Tiny Hobbit like
Found on an isolate island in Indonesia
What was the sequential developmental route for homo habilis into homo sapiens?
Ergaster (Turkana boy) - erectus (Java and Peking man) - heidelbergenesis - sapiens (Knowing man)
Where have other homo erectus remains been found?
Around the Black Sea and in the Kalahari desert
When did the appearance of the Neanderthal man happen?
500,000 - 8000 BCE
When were homo sapiens seen in East Africa?
170,000 BCE
When were homo sapiens seen in Mediterranean?
125,000 BCE
When were homosapiens seen out of Africa?
85,000 BCE
What is it believed died out and were replaced by homo sapiens?
Homo erectus
What is the difference between erectus and sapiens?
- Larger brains (not as large as neanderthals)
- Greater cerebral cortex and testes
- Dependent childhood
- Faster weaning
- Better at endurance running
- Loss of hair to thermoregulate
- Can impose the thumb
- Shoulder girdle anatomy
- Use fire and cook
When was the mesolithic era and why is this important?
12000 - 8000 BC
There was a Sumatra volcano that erupted for 6 years in 71,000 BCE and this lead to the last glacial period - only around 1000-10000 breeding pairs survived and a genetic bottleneck is proposed to of happened
What happened in 8000 BCE?
Neolithic farming
- Metal tools
- Wheel
- Domestication of animals
- Social groups and sheltering
When was the Bronze age?
3000 BCE
- Copper and bronze working
- Weaving
When was the iron age?
800 BCE
- Iron and Steel
When was ancient Egypt?
800 BCE up until 500 AD
What do palaeontologists study and how far back an they go?
Fossils
7 MYA
What do palaeclimatologists study and how far back an they go?
Isotopes and gases
1 MYA
What do geologists study and how far back an they go?
Rocks
4000 MYA
What do genetics study and how far back an they go?
Ancient DNA - very limited and based towards females due to mitochondrial DNA
Also look at living DNA
What do historical experts study and how far back an they go?
Written tests and oral history
5000 Y
What do linguists study and how far back an they go?
3000 Y
What do archaeologists study and how far back an they go?
Tools, ornaments, pottery - 2.5MYA
When did the first movement out of Africa happen?
Around 1.9 MYA
In the first move out of Africa what ancestors moved?
Probably heidelbergenesis and erectus
What were the two main routes taken 1.9 MYA?
Up the Nile Valley
Across the red sea
When did the ancestors arrive in SE Asia?
About 1.7 MYA
When did the ancestors arrive in Europe?
About 1.2 MYA
What did the first migration out of Africa cause?
Probably the origin of Neanderthal man - the nearest human relative
Describe neanderthal origin
- mtDNA is very different to that of humans (202 substitutions opposed to 20 between hominins)
- No mtDNA contribution to modern humans
- Low diversity compared to modern humans/apes
Why were doubts raised about neanderthals and humans being very different species that did not interbreed?
- mtDNA differences are associated with known artefacts
- The Neanderthal characteristic genes could have been lost in genetic drifts in last 30000 years (as they were a relatively small group)
- Research based on small fragments of recent fossils from only a few sites
- Evidence of difference does not reach statistical significance in pair-wise analysis with humans
What is the overall consensus around neanderthals and humans?
They were distinct species (neanderthals arrived in Eurasia first) that co-existed for around 5000 years before neanderthals died out
Could Neanderthals of interbreed with Homosapiens?
- 1-4% of DNA from non-africans appears to have an ancient neanderthal ancestry
- Very crude analysis as there is a common ancestor between neanderthal and humans
- There is anatomical evidence of skeletons with neanderthal and human features
- mtDNA can’t show interbreeding mediated through males
- Whole genome analysis shows more similarity to Europeans than Africans
What examples are there of mixed ancestry/interbeeding from only studying the mtDNA?
- Out of Asia expansion only identified through Y analysis
- Lemba people of SA - Y analysis shows interbreeding of Jews and Bantu that was not revealed by mtDNA
What is the mutliregional theory of human evolution?
After Homo erectus left Africa and dispersed into other portions of the Old World, regional populations slowly evolved into modern humans
- In africa: homo dragster through heidelbergenesis into sapiens
- Out of africa: homo heidelbergenesis/erestus evolved to neanderthalensis and then into sapiens
Evidence favouring heidelbergenesis exists as they has larger brains and were better with tools
What is the out of Africa model?
Asserts that modern humans evolved relatively recently in Africa, migrated into Eurasia and replaced all populations which had descended from Homo erectus
What support is there for the out of africa model?
- Multiregional model of HE to HS would have required a large gene flow
- Human anatomical features were discovered in Africa 130 KYA and 50 KYA in the rest of the world
- Genetic diversity was higher in Africa - longer evolution/larger populations
- mtDNA and Y phylogenies have root in Africa - mtDNA 160 KYA and Y chromosome 140 - 500 KYA
When was the second movement out of Africa?
600 KYA
Who moved out of Africa 600 KYA?
Ergaster - thinner skull bones, reduced supraorbital sulcus (eye cavity)
- Acheulean tools - these tools have symmetry to them and some intelligence must have gone into there development
- Associated with he appearance of G6PD deficiency in Europe - offers protection against malaria
What happened within Africa 200KYA?
Bantu expansion from the Cameroon - replaced most of the African populations in next 2000 years
When was the third out of africa movement?
Around 100 KYA
What is this third migration believed to potentially be?
A founder effect migration as only mtDNA L3 haplotype (a set of genetic determinants located on a single chromosome) found outside of africa
- Some interbreeding could of taken place
What has mtDNA and y chromosomes shown about the TMRCA?
230 KYA - mtDNA
100 KYA - Y
This isn’t when humans developed - X and autosomal loci suggests much older origins of population - 1MYA tailing out to 4 MYA
What are the revised models of evolution?
Single origin model
High migration model
Low migration model
What is the basis of the single origin model?
Few migrate out of Africa so they are less diverse but then out of Africa and in Africa expand (no gene flow)
- Consistent with african frequency data
- Consistent with mt and Y data
- Not consistent with autosomal data and earlier estimate of tMRCA
What is the data supporting/not supporting the high migration model?
High gene flow - archaic populations contribute equally
Consistent with observation of recent and ancient TMRCA
Not consistent with many loci containing rare polymorphisms
What is the data supporting/not supporting the low migration model?
Low gene flow - recognises Africa source but allows for admixture
Consistent with observation of recent and ancient TMRCA
Consistent with many loci having high probability of single archaic origin - especially for haploid that have small effective population number
Why is mitochondrial eve unlikely?
Only if diversity within a population comes from a single time and place which is unlikely as there are influences from the outside
Where do our ancestors come from?
Go back 30 generations there are greater than a billion potential ancestors
Go back 40 generations - there are a thousand billion
What were the invasions carried out by the Barbarians in the 4th century?
Hunnic invasion Visogoth Vandal invasion Frankish invasion Anglo Saxon invasion
When was the Islamic empire formed?
6th century
- Arab invasion from medina
- Persian empire, Syria and Egypt
When were the vikings present?
8th Century
- Scandinavian sailors
- Across Atlantic ocean to Greenland
When was the Mongol invasion?
12th century - lead by Genghis Khan
When was America discovered?
14th Century
When was the slave trade?
15th to 19th century - western europeans into western africa - ships to north and south america
When was New England founded?
15th century
- Spanish and Portugese to the south
- French, British and Dutch to the North (Virginia to Canada)
What and when was penal transportation?
15th Century - people who had commits crimes were shipped of to different parts of the world
When was the industrial revolution?
19th Century - great migration of America (rural south to north)
