Life As We Know ItLife As We Know It

Genetics and the Origins of Humankind

Humble BeginningsHumble BeginningsLife (4000 mya)Bacteria (3900 mya)Algae (1600 mya)Plants (1300 mya)Vertebrates (510 mya)Mammals (114 mya)

HominidsHominidsPrimates evolved ~95 myaGreat Rift Valley:

separates African animal populations diverse ecological conditions

Hominids diverged from Apes on border of forested and savanna environments

Homo sapiens sapiens ~150,000 ya

Inefficient means of travel (except in savanna)

Knuckle-walkingAdapted for arboreal lifestylePredator avoidanceAvailability of handsCooling and birthing

BipedalismBipedalism

Rapid encephalisation of the brain: 1 to 3 lb. brain in only 2 m years

Machiavellian intelligenceClimate changeBallistic huntingLanguage and group sizeSexual selection

Origins of the MindOrigins of the Mind

DNA & base pairs: Adenine & Thymine, Cytosine &

Guanine Shared among all life

Genes are sequences of DNA Build specific proteins Different forms of a particular gene

are called alleles

Genetics: The Machine at Genetics: The Machine at WorkWork

ChromosomesChromosomesStrings of genes23 pairs:

23 paternal copies 23 maternal copies

Ordered by size (imperfectly)

Sex ChromosomesSex ChromosomesX chromosome:

All humans have at least 1 copy Females have 2 (homogametic)

Y chromosome: In humans, only males have a copy Males have 1 X and 1 Y

(heterogametic) Little genetic information, “SRY”

Mendelian HeredityMendelian HeredityChromosomes separate (segregate)

during gamete formation

Dominant & recessive genes

Exception: Mitochondrial DNA

Mathematics of InheritanceMathematics of InheritancePunnett squares:

Female gametes

Male

gam

ete

s T

T

T

Female gametes

Male

gam

ete

s T

T

t

t t

TT TT TT

tt

Tt

Tt Tt Tt

The Wrap-UpThe Wrap-UpEvolution of life on EarthGreat Rift ValleyArboreal & savanna environmentsBipedalismEncephalisation & origins of the mindDNA, genes, chromosomes (incl. sex

chromosomes)Mendelian heredity & Punnett squares

Things to ComeThings to ComeProblems of survival:

Food acquisition & selection Habitat & environmental preferences Predators & environmental dangers Senescence