HUMAN EVOLUTION

Trends in Human Evolution

1. Bipedalism (upright walking) 2. Opposable thumb (precision grip and power grip) 3. Changes in brain and behavior (language, culture) 4. Changes in dentition 5. Binocular vision 6. Temperature regulation IMPROVEMENTS IN THE TRAITS MUST PROVIDE A REPRODUCTUVE ADVANTAGE!!!

Origin of Life

FORMATION OF EARTH o 4.5 billion years ago LIFE ON EARTH BEGAN o 2.5 billion years ago 3 POSSIBILITIES FOR THE ORIGIN OF LIFE: o extraterrestrial origin o special creation o evolution

Evidence of Evolution

FOSSIL EVIDENCE : most direct evidence; 10,000 yrs - billions of years old BIOGEOGRAPHICAL EVIDENCE : study of distribution of plants and animals and how life is influenced by the mix in certain locales. Darwin ANATOMICAL EVIDENCE : anatomical similarities between organisms BIOCHEMICAL EVIDENCE : all organisms use same biochemical molecules (DNA and ATP, enzymes) DNA similarities provide evidence of relatedness MOLECULAR CLOCK : using time and DNA changes to determine relatedness of 2 species

Evolution: Basic Terms

THEORY OF EVOLUTION: modifications in genes that are passed from parent to offspring result in changes in future generations. These changes lead to greater diversity among organisms. EVOLUTION: changes in an organism population's characteristics over time NATURAL SELECTION: mechanism of evolutionary change resulting in adaptation to the environment

Temperature Regulation:

Why do we need to stay cool? PROTECT OUR LARGER BRAINS • ADAPTATIONS: bare skin and watery swear o WHAT DROVE THESE ADAPTATIONS? ♣ 3 mya: Landscape changed! Earth cooled, drier Africa, Savannah grasslands replaced woodlands (food and water) ♣ 2.6 mya: hominids added meat to diet, hunting (and creating tools) • elevated activity levels leads to risk of overheating o WHEN DID THESE ADAPTATIONS OCCUR? ♣ About 1.6 mya: fossil evidence.. Homo Ergaster ♣ About 1.2 mya: skin color darkened... MCIR gene originated o WHAT TYPE OF CHANGES? ♣ DNA evidence of skin differences between humans and chimps ♣ Humans: fragile hair keratins, skin structure, and barrier proteins

• Future possibilities:

o Changes due to computes, video, smart phones o Change our genes? New species? Symbiosis with machines • Technology/Culture change at a faster rate than we do!!

• Currently evolving:

o Lactose enzyme for digesting cows milk o Possible gene variants against malaria and HIV

Bipedalism

walking erect on 2 feet • When: 4.2-3.9 mya (Australopithecus) •Theories and Advantages: o Jungle to savannah adaptations o Long distance travel o Feeding postures, carrying food/weapons/tools over long distances, ability to see distances o Others: warning displays and vigilance against predators, phallic display, access to deeper water

Before humans:

• 65 mya: common ancestor was an Archonta - arboreal, insectivorous, nocturnal mammal • 55 mya: Early Primates evolved, fossils o Binocular vision, opposable thumbs, foramen magnum • 30 mya: Old World Monkeys • 15 mya: Apes diverged, 10 mya - orangutans diverged • 8-9 mya: Hominins diverged (gorillas and early humans) • 7 mya: chimps diverged (based on DNA differences) • fewer DNA differences = more recent divergence

How we are evolving now

• Beneficial gene mutations evolve very slowly! • Recently evolved: o Genes for light skin in non-Africans o High altitude variant in Tibetans (within 3000 yrs)

Comparing Humans and Chimps

• DNA : 98.8% same • Chromosome 2 • Brains: humans have larger brains, surface area, frontal lobe • Language: Humans - vocal cords, tongue/lips, chins • Diet: human intestines, chimp teeth, meals • Walking: pelvis shape, hip size, feet and toes • Eyes: both use binocular vision, color differences • Tool Use: 1960, chimps make spears, use stones • Sociability: talking (humans) v. grooming (chimps)

Changes in Dentition

• Dentition: teeth and jaw • Diet: insects fruits/ leaves mixed with meat • Agriculture, cooking, use of tools made food softer • Human teeth and especially the jaw are smaller • Human problems: tooth decay o Overcrowding and malocclusion

Taxonomy: Where do we fit in

• Domain: Eukarya (single or multi celled organism) • Kingdom: Animalia, Metazoa (plant, bacteria, fungi) • Phylum: Chordata (body plan - our spinal cord) • Class: Mammalia (share 3 characteristics) • Legion: Cladotheria (live birth w/o shelled egg) • Cohort: Eutheria (embryos and placentas) • Order: Primates (anatomical details) • Family: Hominidae (primates that walk upright) • Tribe: Hominini (humans and 2 types chimps) • Genus: Homo (all humans.. 2.5 million yrs old) • Species: Homo sapiens (extinct and present) • Subspecies: Homo sapiens sapiens (modern)

Examples of Biochemical Evidence

• Genome sequences between species are very similar • DNA sequences mutate at a steady slow rate o 1% DNA changed between chimps and humans in 6m years • Faster DNA changes indicate positive selection • Some gene mutations indicate human evolution: o HAR1: neuron pathways in cerebral cortex o HAR2: fetal wrist and thumb development o FOXP2: speech muscles (also present in Neandertals) o ASPM: controls brain size (tripled in human evolution) o AMY1: digestion of starch (complex foods available) o LCT: digestion of milk sugar (still evolving in humans)

Binocular Vision

• Present in all primates • BINOCULAR VISION: both eyes used together, anterior • Originally: monocular vision (eyes on side of head) • Later: forward-directed eyes (binocular vision) o Better detection of shapes and movement in 3D • Later modifications: response to color and light variations • Advantages: o Depth perception o Motion detection o Hunting

Forming Larger Cells

• Small organic molecules clumped together to form MACROMOLECULES - nucleic acids, amino acids (RNA and DNA) • Lipids and proteins come together to form a membrane, leading to a PROTOCELL. Protocells are capable of metabolism but not reproduction. TRUE CELL: can reproduce, PROKARYOTIC & lacking a nucleus... nuclei and multicellularity gradually evolved

Large Brains

• Tripled in size over 7 million yrs (most gains in last 2 million yrs) • Genes: brain size, more stem cells, larger space • Also due to: improved diet, social interactions • BRAIN MODIFICATIONS AND BEHAVIOR COMPLEXITY BECAME CLOSELY LINKED o Culture and language o Dietary needs (meat) o Technological prowress • MOST GAINS ARE IN NEOCORTEX o Thought, planning, problem solving, communication

From Hominins to Humans

•ARDIPITHECINES (Ardi): 4.4 mya, chimp-sized o Bipedal but climbed trees, small brain •AUSTRALOPITHECINES: 3.7-1.5 mya, Lucy o Bipedal, hairy skin, small brain, used stone tools o Ape-like above waist, human-like below waist •ARCHAIC HUMANS: 1.5-.25 mya, gradually increasing brain size from 350cc-1000cc (Homo habilis to Homo ergaster..) tool use •MODERN HUMANS: 200 kya: Cro-Magnons: common ancestor between ethnic groups alive today. o Advanced tools, accomplished hunters, culture, migrated

Large Brains Lead to Culture

•CULTURE: classify experiences with symbols and act creatively o LANGUAGE: both structural and neural components require for speech o Human made shelters 60kya o Spiritual rituals and burials o Rise of the GRANDPARENTS ♣ Directly contributed to the # of offspring, longer life, group dynamics • Large/ more complex brains require more time to develop leading to longer childhoods and greater populations. Larger populations are major drivers of new behaviors.

Humans are Primates

•DNA data suggests: o common ancestor for humans and primates existed 7 mya in Africa o Humans first evolved in Africa and migrated to Eurasia •90% similarity in DNA •Characteristics of primates: o Mobile forelimbs and hindlimbs o Binocular vision o Large, complex brain o Reduced repdocutive rates •Skeletal differences humans upright walkers

Opposable Thumb

•Evolved from Homo Habilis through to Homo Erectus •RELATED TO HAR2 GENE •LED TO PRECISION GRIP AND POWER GRIP • When hands were free from walking • DIRECTLY LINKED TO TOOL DEVELOPMENT • Reproductive advantage • Some animals have big toes • CHIMPS: thumbs are weak and shorter, creating a less firm grip

Control of Fire

•Fossil evidence o 400 kya by Neandertals o 800,000-1 mya (Homo erectus) •Lead to cooking (began 250-800 kya) o Releases more nutrients and calories, easier to digest o Gut and dentition changes (possibly larger brains) •Developed social dynamics of community •Protection from nocturnal predators, warmth •Brought day into night (sleep patterns) •No evidence that FIRE contributed to: o Migration to cooler climates (800 kya) o Eating meat (1.5-2.6 mya)

Earth's Atmosphere 2.5 billion yrs ago

•NO OXYGEN: INORGANIC MOLECULES...hydrogen based gasses such as water vapor, methane, nitrogen ENERGY: from sun and lightning caused spontaneous formation of SMALL ORGANIC molecules from inorganic molecules •Organic molecules have been found on meteors

Our Inner Neanderthal:

•Neandertals (originated: Europe 100-300 kya) o Stocky, massive brow region, large brains and teeth o Culturally advanced: tools, used fire, symbolic thinking •Neandertals and Homo sapiens interbred 50-80 kyda •1-4% Neadertal genes in the human genome o related to keratin (skin and hair) o type 2 diabetes, lupus, cirrhosis, Chron's disease o Improved immunity and increased allergies •Very little Neandertal DNA on X chromosome o Different species or barely compatible