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Evolutionary Biology

Human evolution

QuestionAnswer
Humans on the tree of life • Primate phylogeny based on numerous derived characteristics • Clearly most related to great apes (hominidae) • human most related to chimps • molecular clock - separation 5.4 mya
Primate evolution Within the great apes (Hominidae) – four taxonomic groups (tribes) Humans, extinct ancestors and related races/species = Hominini
Hominini dispersal • Homo genus range expansion out of Africa approx 1.8 MYA • Homo erectus like forms (archaics) spread across the world • Resolving between these forms/species remains controversial • H. erectus - surviving 1.8 million years
What makes us human? - increased cognitive abilities (brain size enlarging) - tool use, handywork - bipedalism - hunting/farming - establishing society/hierarchy
Genetic differences Humans: 2 pairs of 23 chromosomes Chimps: 24 chromosomes Chimp genes disabled in humans, causing variation
The origin of humans 1) Out of africa - humans expanded out of africa 2) Multi-regional evolution - gene flow allows evolution in different places 2% neanderthal DNA in non-african humans
Variation among humans Compare genetic diversity in apes with that amongst humans - mitochrondrial DNA Subdivided into race Subtle differences exist in alleles frequencies at specific loci between populations Natural selection shapes human variation
Lactose intolerance Broken down by lactase, yet around 70% of humans cannot digest lactose Lactose tolerance - lactase persistance gene
Human skin colour Dark skin = ancestral in humans – protects against Ultra-Violet radiation (UV) Pale skin evolved – avoids Vitamin D deficiencies at higher latitudes Related to UV levels regionally
Summary • Hominins most closely related to Chimps (5.4 MYA) • Humans are the last of the Hominins • Tool use, relative brain size, bipedalism and gene expression differences make us markedly different from other primates
Summary • Modern humans – very recent expansion out of Africa – with a small amount of introgression with archaic hominin forms • Very limited genetic variation between humans worldwide • But selection has, and still is, driving variation
Created by: rose.coo
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