L9. Human Evolution Flashcards
Where are humans in the tree of life
- At broadest level we are part of Eucarya
- kingdom: animalia
- phylum: chordata (symetrical, backbone)
- class: mammalia (mammary glands, fur/hair, live birth)
- order: primates
- genus: homo (only remaining)
Lamarck’s contribution
- first to suggest that apes and humans had a shared evolutionary history
Reasons it was hard for Darwin to prove anything
- no DNA evidence
- no fossil record (until the 1800’s no fossils found of ancient human species, only a few stone tools)
Carl Linnaus
- first to connect humans to apes
- 1735
- put us in a the same order
- no theory of evolution at the time
Origin of the fossil record
1820: first homid skull fossil found in Belgium
- started a big hunt for fossils
- Lots of work done in Indonesia, found very primitive “human-like fossil” (homo erectus)
- Northern Kenya: fossil jackpot, lake and river sediments, well preserved fossils
Fossil record
- provides snapshots of the past which, when assembled, illustrate a panorama of evolutionary change over the past 3.5 billion years
- shows that our lineage split from chimps around 5-13 ma
- large amount of species in genus homo
- big branches: different species, some lived in the same area
Human tree (order)
- (4.2 - 2 Ma) Australopithecus: “Lucy”, small brains, made tools, change in diet, lived in Africa
- (2.4 - 1.5) Homo habilis: “handy-man” brain getting bigger, smaller teeth, made stone tools, lived in Africa
- (1.9 Ma - 150,000 years) Homo erectus: big brains, tools, hunters, fire, culture?, most successful species to date, lived in Africa, East and west Asia
- (1.2 Ma - 800,000 years) Home antecessor: unclear, sister species to to H. sapiens, suggests another lineage of human evolution, lived Western and Southern Europe
- (700,000 - 200,000 years) Homo heidelbergensis: overlapped/evolved, lived in Asia, Europe, northern Africa
- (200,000 - 50,000 years) Home florensis” “the hobbit”, insular dwarfism, primitive features, lived in Indonesia
- (400,000 - 40,000 years) Homo neanderthalensis: sister species to us, bred with H. sapiens, survived many ice ages, had many technologies we recognize, lived in Europe and Central Asia
Homo Sapeins
- 300,000 - today
- only extant species in the Homo genius
- skull morphology has changed distinctively over time
- evolved in Africa and left around 185,000 years ago
- interacted and interbred with other Homo species
Progression of Evolution
- not a straight line
- evolution associated with physical (larger brains) and technological (use of tools) changes that opened up new niches
- environment changing (climatic variability and extremes)
- morphological traits make it hard to know if different species (ex. compare Shaq to Simone Biles), this solved by DNA testing
Ancient aDNA
- sequenced the neaderthal genome
- theoretical upper limit of 1.5ma
- can use a tiny sample, then a pcr test lets us amplify and make copies then reassemble ancient genome
- aDNA can be so intact in that they were able to compare the regions of mitochondrial DNA to construct a phylogeny representing the evolutionary history of their samples. Means potentially we don’t need fossils to get aDNA
Neanderthal Genome Project
International effort to sequence the entire genome of H. neanderthalensis from two bones. Took 4 years and had to sort through degraded and contaminated aDNA
Methodologies:
- used computer programs to eliminate bacterial DNA from sequence
- resulting sequences were compared to modern H. sapiens DNA and mapped by comparison to the modern human genome
Discoveries:
- likely started with a very small founder population
- had a gene mutation we believe to be required for complex speech
- produced fertile offspring with humans
The Denisovans
- interbred with Humans and Neanderthals, lots of cross over in DNA
- particularly pronounced in East Asian populations
Homo sapiens Family Tree
- our most recent ancestor only lived 2000-3500 years ago
- if you go back far enough everyone ancestry trees converge
- most common ancestor of all humans probably lived in East Asia
Will space change our DNA?
- space radiation may lead to more mutations
- Nasa did studies with twins and when astronaut came back 7% permeant difference in their epigenome
Modern Genetic Diversity
- Highest diversity in Africa, lower in Europe, lowest in South America
- greater proportion of rare alleles in African populations
- greater proportion of deleterious mutations in Europeans populations
