25- Evolution of You Flashcards
who provided the first attempt to classify humans in comparison to animals, how did he classify
Linneaus 1735
- divided homo into 6 subgroups
1. ferus (feral children)
2. monstrous (people with physical deformities)
3. americanus (american indigenous)
4. asiaticus (populations from asian countries)
5. eropeus (europeans)
6. afer (africans) - Linneaus further divided homo based on “principle traits” (racist)
other proposed ideas before theory of evolution
A number of scientists between 1774 and 1817 had ideas that linked apes and humans:
- James Burnett - thought apes as wild variants of humans
- Delisle de Sales - thought apes were an intermediate between humans and animals
- Constant Dumeril- described apes based on physical relatedness to humans
- George Cuvier- placed apes as animals closest to man, but denied evolution as the root when darwin published his work
what was darwin’s theory on human evolution
In 1871, Darwin proposed that shared anatomical traits between humans and apes meant that they had a recent common ancestor
the fossil record: a timeline through history
- up to 1800s, no fossils of ancient human species
- in 1829 and 1848: skulls found but not recognized
- 1856: bones found in Germany
- 1859: darwin publishes “on the origin of species”
- 1864: geologist examined the skull from Germany–> proclaimed it was a different species based on the morphological characteristics of the skull… first human species identified besides our own! Named “homo neanderthalensis” (after where it was found)
- 1886: 2 preserved Neanderthal skeletons found in Belgium, found alongside extinct Pleistocene mammals –> paradigm shift: could no longer deny ancient age of Neanderthal skeletons.
Identification of many different species in homo followed form 1891 to 2010
what did we previously believe about human evolution
We once believed there was a straight line from ape ancestor to us today
- once single evolutionary branch
- homo species did not go extinct, instead they became the next species in the homo genus
This gave us the “march of progress” graphic
whats wrong with the “march of progress”
- implies continuous progress in homo genus
- doesnt show failed and extinct lineages
- doesn’t show hybridizing
issues using morphological traits to identify human species
- fossil record = fragmented
- difficult to tell apart natural variation with species from differences separating species
issues using DNA to identify human species
- half life of DNA is 521 years
(takes 521 years for half of all DNA in a given sample to break down) - most recent extinction of ancient homo species was 24,000 years ago –> we couldn’t extract DNA
what is aDNA
= ancient DNA
- age is around 150 years old to millions
- oldest found so far: 800,000 years old
problem with analyzing aDNA
- oldest aDNA sequenced so far was 430,000 years old
- could only sequence 0.1% of the entire genome they set out to build –> rest of DNA was too degraded
how can we analyze DNA which is degraded
- PCR lets us takes small bits of DNA and make lots of copies
- we know which regions of DNA are more likely to break down over time –> can design models to take this into account when reconstructing DNA sequences
- can build ancient genomes from fragments by comparing them to modern descendants
which part of the body is best to extract DNA
- protected structures (such as inside teeth and bones)
- more difficult for bacteria + environment to degrade
- DNA extracted from amber can still theoretically be analyzed millions of years after being entombed
(limited to plants, bacteria, anthropods)
example of mistakenly identifying aDNA
- due to modern contamination, we thought human DNA was dinosaur cytochrome b
- original researchers did not verify that their “dinosaur sequences” were not found in modern descendants (like birds)
what is the Neanderthal genome project
= international effort to sequence the entire genome of H. nethanderthalensis
(like the human genome project)
- began 2006 –> almost completed in 2013
- took only 4 years, and had to sort through degraded and contaminated aDNA
what did we discover about H. nethanderthalensis from the neanderthal genome project:
- H. nethanderthalensis likely started with a very small founder population of 3000 individuals
–> coincides with the “out of africa” migration theory - H. nethanderthalensis had a gene mutation in FOXP2 we believed to be required for complex speech
(Neanderthals may have had a language like us)
