1. Human Origins and Evolution
Bio HL
Human Origins and Evolution

2. Full Classification of Humans
Kingdom - Animalia
Phylum - Chordata
Class - Mammalia
Order - Primata
Family - Hominidae
Genus - Homo
Species - Homo sapiens
subspecies - H. s. sapiens

3. Humans are primates??
Primates are an order of mammals including monkeys, tarsiers and lemurs
We share this classification because we have similar anatomical features that are characteristic of that order
Grasping limbs with long fingers with a separated opposable thumbs
Sensitive fingers with nails
Mobile arms with shoulder joints that allow movement in three planes
Our arms have a shoulder girdle that allow weight to be transferred via the arms
Stereoscopic vision with forward facing eyes on a flattened face giving overlapping fields of view
Excellent hand-eye coordination
Skull modified for upright posture

4. Anatomical and Biochemical Evidences
98% of Human and Chimpanzee DNA is the same
Fossils of human intermediate species have been found
Similarities with how we raise our youth for a relatively long time before being considered an adult

5. Hominid Fossil Trends Hominids are members of the family Hominidae
Includes humans
Primary feature – bipedalism
Humans are currently the only species in this family but others have existed in the past
Fossils show two major trends:
Increased adaptation to bipedalism
Increased brain size to body size ratio

6. Other Fossil Changes and Trends
Enlargement of brain and taller and more erect structure.
The spike connection to the skull becomes more central to balance centre of gravity.
Pelvis changes to support organs in walking.
Pelvis shorter and broader to attach walking muscles.
Legs become stronger and longer while arms become shorter and weaker.
Knee can now be fully straightened.
Foot forms more of a platform and rigid shape without opposable toe.

7. Hominids
Australopithicus afarensis: million years – ape-like face
A. africanus: million years – flatter face, larger molars for plant based diet
A. robustus: million years – very large molars, bones and skull
Homo habilis: million years – smaller teeth and jaw for meatier diet, first with tools, size like humans
H. erectus: million years – more complex tools so meat significant part of diet and changed teeth.
H. neanderthensis .5 million years – larger brains and bones, larger teeth and jaw, shorter limbs for the cold
H. sapiens

10. Dating Fossils
Radioisotopes – radioactive isotopes (have different numbers of neutrons) of a chemical element
As an atom of a radioactive isotope decays, it changes into another isotope and gives off radiation
Most common radioisotope used are 14C and 40K
The rate of decay varies between different isotopes
Half-life = the time taken for the radioactivity to fall to half of its original level

11. Decay Curves
Radiocarbon dating – the percentage of surviving 14C atoms in the sample is measured
In potassium-argon dating, the proportions of parent 40K atoms and daughter 40Ar atoms are measured.
The age in half-lives can be deduced from the decay-curve
Half-life of 14C is 5730 years (useful for 1,ooo to 100,000 years old)
Half-life of 40K is 1250 million years old (useful for samples older than 100,000)

12. Decay Curve Examples

13. Fossil Record – as a whole
Missing major portions of all species that have ever existed – very incomplete
Only a tiny portion of animals became fossils
REGARDLESS – shows how intermediate species have developed
Humans => Hominid trends
Horses => transition from 4 toes to only one

14. Horse Toes!!

15. Hominid Fossil Record Consists of only bones and teeth
Hominid fossil record is FAR from complete – “missing links” are still missing
Small findings can lead to major changes in theory because we don’t completely understand how we transitioned from species to species
Australopithecus species shares similar characteristics to Ardipithecus ramidus and Australopithicus afarensis
Dating of fossils of the three species suggest that they did not co-exist but form an evolutionary lineage

16. What spurred the evolution of man?
Climate changes in Africa – transition from a woodland to a drier, more sparse environment
Switch from tree-dwellers to land-dwellers came with the depletion of the forests
Later, Africa became cooler – advantage to groups of hominids working together to hunt, use of tools, etc

17. Hominid Diet
Earliest hominids (Australopithecus) were only slightly larger in body/brain size than apes. They had powerful teeth and jaws indicating a primarily vegetarian diet.
Later hominids (once Africa cooled) Homo hominids began developing tools. With this came the ability to eat meats. Transition from vegetarian to omnivorous diet.

18. Advantages of Eating Meat
More meat = more protein = more energy
Meat = more fat = more energy
More meat + more fat = larger brain capability and size
Natural selection will begin to work and favor individuals with the biggest brains and intelligence
Will also favor individuals who are able to work together

19. Advantages of Culture Learn to hunt and work together
Language
Learn to make better tools – better survival
Learn to limit environment’s influence : make clothing, build shelters
Cost = mature individuals take longer time to develop, bigger investment

20. Genetic and Cultural Evolution
Cultural evolution – able to slow and even hamper the effects of genetic evolution
Language
Tool making and other skills
Religion and art
Medicine
Genetic evolution
Involves inherited differences and allele frequencies

21. The Hardy-Weinberg Principle and NeoDarwinism

22. Neo-Darwinism
Synthesis of our understanding of Natural Selection blended with our understanding with genetics
Idea that mutations occur all the time
Changes to our genes “mutations” occur
Can lead to new potential alleles and phenotypes IF they are inheritable changes

23. Gene Mutations vs Chromosomal Mutations
Gene mutations – a change that occurs in a particular point in the DNA
Affects a single gene – a single protein malfunctions
Examples:
PKU or phenylketonuria
cystic fibrosis
Chromosomal Mutations – a change that affects part or all of a chromosome
Klinefelter’s syndrome (caused by non-disjunction of the X chromosome, leads to XXY)

24. Hardy-Weinberg Principle
Evolution involves changes in allele frequencies
Hardy-Weinberg equation is used to calculated the changes in allele frequencies
The total frequency of the alleles in the population is 1, so… p + q = 1
Where the two allele possibilities in a population are represented by p and q

25. Hardy-Weinberg Continued
If random mating occurs the chances for inheriting two copies of the p allele is = p x p or p2
The same is true for q = q2
The same can be said for the heterozygote = pq
In all it’s glory, the Hardy Weinberg Equation
p2 + 2pq + q2 = 1

26. Seriously… What did I just read???
Hardy-Weinberg Assumptions
Random mating must occur
Natural selection will not cause a higher mortality rate for one allele over the other
There is no mutation occurring
The population isn’t small
There is no immigration or emmigration

27. Example 1 Genotypes of pure breeding varieties are TT and tt
An experimental pea plant is established by sowing seeds of pure breeding tall and dwarf varieties in a ratio of three tall to one dwarf. The plants are allowed to disperse seeds naturally. What proportion of tall and dwarf pea plants are expected after several generations?
Genotypes of pure breeding varieties are TT and tt
Frequency of T (p) is 0.75
Frequency of t (q) is 0.25
Frequency of dwarf plants (tt) = =
Frequency of tall plants (TT or Tt) = 1 – =

28. Example 2: 461/1600 = (tt) = 0.288 SO 0.288 = p2 p = 0.537
The gene that controls the ability to taste (PTC) has two alleles: ability to taste (T) and non-tasters (t).
1600 people where tested in a survey.
461 were non tasters (tt). What are the frequencies of the p and q alleles?
461/1600 = (tt) = SO = p2
p = 0.537
If q = frequency of the T allele,
q = (1 – p) = 0.463

29. Classification and Phylogenetics

30. Biochemistry and Common Ancestry
All living organisms use DNA or RNA as their genetic material
All use the same basic universal code
All use the same 20 amino acids in their proteins
All use left, and not right-handed, amino acids

31. Phylogeny
Tracing evolutionary history, links and origins is known as phylogeny
Studied by comparing the protein structure or other biochemical that they contain
Typically, results match the existing classification of the group

32. Evolutionary Clock
Differences in base sequences of DNA (and therefore the amino acids sequence of a protein) accumulate gradually over time.
Accumulation occurs at a roughly constant rate – allows us to “time” how long ago mutations occur and how long ago a species split from a common ancestor

33. Clades, Cladograms and Cladistics
Node – show groups of organisms which are related
Share common ancestry
Also known as a clade
A clade is a group of organisms that evolved from a common ancestor
Can be large or small groups
Can have far distant relatives (large groups)
Can have close relatives (small groups)
Tree diagrams showing clades are called cladograms
Study of classification is known as cladistics