BIO 3061 BIOLOGICAL EVOLUTION OF HUMANS

Question 1

What are being used to compare species and establish evolutionary relationships

Answer 1

DNA sequencing comparisons, mitochondrial DNA and Y chromosome DNA are being used to compare species and establish evolutionary relationships.

Question 2

What is strata

Answer 2

Layers of rock where fossils are usually found. Oldest strata are at the bottom and newest strata are on top.
See progression of complexity as organisms evolve from earliest forms to more complex forms recently.

Question 3

Relative dating

Answer 3

-first main way of finding out how old a fossil is
-arranging fossils in chronological order from oldest to youngest without assigning dates to them.
-lower layers of strata are older than higher layers
-sequence of evolutionary changes can be used
-timing of events such as volcanic eruption or earthquake help to place in correct time span.

Question 4

Absolute dating

Answer 4

-second main way of finding out how old a fossil is
-finding out it’s age
-done with radiometric dating
-based on radioactive chemical elements (isotopes) .
-isotopes decay over time at a constant rate because of half-life
-most common isotope to date fossils are carbon-14 with half life of 5730 years & used to date fossils less than 50 000 years old.
-potassium-40 with half life of 1.3 billion years and is used for older fossils that may be millions of years old.

Question 5

Nuclear of genomic DNA

Answer 5

DNA is found in nucleus of every living cell. It carries the genes of the organism it is found in. Also a smaller amount of DNA in mitochondria of every cell and in chloroplasts of plant cells.

Question 6

DNA extraction from fossils

Answer 6

-challenging process
-DNA strands break down over time into smaller pieces so less likely to reconstruct entire strands.
-DNA is damaged during process that turns the bone into a fossil
-contamination of lying in the ground for thousands of years

Question 7

Explain DNA sequencing in relation to human evolution

Answer 7

-dna has been sequenced so that the order of nucleotide bases in dna has been determined
-indicates the order of amino acids in proteins coded for by the bases
-dna from different species can be compared to see how similar they are
-dna will be very similar if two species are very closely related
-e.g. human genome and chimpanzee has been sequenced and found to be 98% identical.

Question 8

How are evolutionary relationships between different species established

Answer 8

-generally there are very small changes or mutations between one generation and the next
-over a long time frame, mutations accumulate.
-looking at the differences in dna it is able to determine the differences between two species and how long ago they shared common ancestor.

Question 9

Why is mitochondrial DNA different to nuclear DNA

Answer 9

It is passed along from the mother to child and so it is used to track evolution through the female line only. (Maternal evolution)

Question 10

Give the two suborders that the primate order consists of

Answer 10

Prosimians
Anthropoids

Question 11

Primates

Answer 11

-Humans belong to order called primates
-primate ancestor first appeared in palaeocene epoch 65 million years ago.

Question 12

Evolution of primates

Answer 12

Question 13

What are primates

Answer 13

-mammals
-bear live young
-warm-blooded (homeothermic)
-suckle their young on milk secreted from mammary glands
-hair and sweat glands
-four types of teeth : incisors, canines, premolars, molars
-four-chambered hearts

Question 14

Early primates

Answer 14

-small rat like animals
-nocturnal and arboreal (mostly in trees)
-first true primates evolved 55 million years ago or earlier near beginning of eocene epoch
-fossils found in notth america, europe and asia

Question 15

Major physical characteristics of primates

Answer 15

-prehensile (grasping) hands for holding and manipulating objects
-nails instead of claws
-binocular, stereoscopic vision
-good eye-hand coordination
-large brains and eyes
-tails for balance
-colour vision and good night time eye sight
-mobile wrist, elbow and shoulder joints
-bony ridges to protect eyes
-oestrus cycle rather than definite breeding season (some only)

Question 16

Prosimians

Answer 16

-Lorises and lemurs evolved in eocene from ancestral primate ancestor
-look like first primates
-unusual group are tarsiers evolved in eocene and became specialized as nocturnal tree-livers
-enormous eyes
-specialized as nocturnal feeders
-mix of prosimian and anthropoid traits

Question 17

Anthropoids

Answer 17

-incl. all of the remainder of the living primates, old world and new world monkeys and the apes

Question 18

The monkeys

Answer 18

-evolved in oligocene abput 36 million years ago

-OLD WORLD MONKEYS
-africa and asia
-africa and asia are part of the “old world”
-babboons, macaques, colobus, langur monkey

-NEW WORLD MONKEYS
-only in the americans
-central and south
-central and south america is known as the new world
-spider monkey, howler monkey, tamarins, marmosets

Question 19

The great apes

Answer 19

-evolved around 20 million years ago
-proconsul is a key fossil
-monkeys have tails and apes don’t

Question 20

Proconsul

Answer 20

-means before consul
-fossil was named after a popular chimpanzee in the London zoo
-Consul had no tail, or pelvic pads &skeleton suggests that it walked along tree branches

Question 21

Features that differentiate apes from monkeys

Answer 21

• semi-upright to upright posture
• larger more complex brain than monkeys
• greater shoulder mobility than monkeys
• rib cage flattened from front to back
• cusps on their teeth (only human and apes) Y-5 molar shape

Question 22

Two main groups of locomotion

Answer 22

-arboreal locomotion
-ground locomotion

Question 23

Two forms of Arboreal locomotion

Answer 23

-Quadrupedalism : walking on all fours, as in lemurs. Most primitive form of locomotion. Leaping and clinging.

-Brachiation : body swings from the arms. Gibbons are most striking brachiators. Monkeys spend some time using brachiation.

Question 24

Three forms of ground locomotion

Answer 24

-Quadrupedalism, as in babboons
-Knuckle walking, chimpanzees and gorillas. Body rests mainly on legs while knuckles provide additional support.
-Bipedalism, walking upright on two legs. Habitual, as in humans. Temporarily as in apes.

Question 25

Early primates

Answer 25

-arboreal
-grasping hands and feet
-long mobile limbs
-quadrupedal
-binocular vision
-nails rather than claws

Question 26

Prosimians

Answer 26

-similar characters to early primates
-tarsiers have some features of anthropoids

Question 27

New world monkeys

Answer 27

-prehensile (grasping) tail
-quadrupedal
-arboreal
-widely seperated nostrils

Question 28

Old world monkeys

Answer 28

-tail not prehensile
-quadrupedal
-mix of ground and tree living
-nostrils close together

Question 29

Great apes (pongins)

Answer 29

-brachiating
-no tail
-gibbons live in trees; others partly or mainly ground living - knuckle walkers
-flattened noses
-brow ridges

Question 30

Hominins

Answer 30

-humans and closely related forms
-bipedal
-large cerebral cortex
-reduced canines
-nose, chin prominent
-reduced brow ridges

Question 31

Name important differences between humans and apes

Answer 31

• human’s S shaped spine is different from the gorilla’s spine
  -human legs are much longer in proportion to arm length, whereas gorilla has very long arms relative to it’s length
  -human pelvis is much shorter and wider than gorilla
  -human limb bones are straighter than gorilla
  -human skull has rotated to fit upright posture

-gorilla pelvis has forward angle
-femur is angled forward in gorilla whereas human has a more vertical femur
-end of human spine is curved forward
-head of human femur is much longer than gorilla’s femur
-gorilla’s femur is curved compared to human’s
-australopithecine femur is intermediate between human and gorilla

-human femurs are wide apart while our knees are close together. Therefore valgus angle between the knee and hip is much greater in humans than apes. This is because the body weight needs to be shifted closer to the center of gravity

-pelvis long and narrow in chimpanzees to allow for sloped spine to attach
-in humans, the short, wide pelvis allows for spine to attach to suit upright posture

-human foot is arched, ape foot is not
-apes have gap between big toe and the rest, which is useful for grasping tree branches

-gorilla thumb is partly opposable.
-human has far more opposability than gorilla’s
-human have power grip and precision grip whereas gorilla’s lack it

-gorilla head sits forwards of vertebral column. Neck muscles are massive to hold it in place.
-gorilla jaw muscles are much larger than those of humans
-human head sits on top of vertebral column. Requires less muscle to hold it in place.

-gorilla jaw is long and U shaped with parallel sides
-human jaw has semicircular curve
-gorilla teeth are strongly differentiated into canines and large incisors.
-human teeth are similar to each other.
-differences in human and gorilla teeth are mainly related to diet

-human brain is larger than gorilla brain
-human brain has much enlarged frontal area (where learning occurs)
-human has larger visual area in the brain than the gorilla

-entry hole for spinal cord (foramen magnum) is at rear in ape’s skull.
-foramen magnum has rotated and sits on top of spine, tucked under skull, in humans

Question 32

Explain the difference in the foramen magnum of humans and apes

Answer 32

It is at rear in the ape’s skull, whereas humans has it rotated and tucked under the skull so that it sits on top of the spine.

The skull is balanced on the vertrbral column via two projections known as occipital condyles. In humans the occipital condyles are positioned forwards, while in apes they are much further back.

Difference in humans enables spine to support fully upright posture.

Question 33

Characteristics of australopithecus

Answer 33

-Slender (gracile) build
-arms longer than the legs
-curved hands and feet but walked bipedally
-flat face
-brain size still about same size as chimp
-showed sexual dimorphism
-males are larger than females

Question 34

Important point to remember about our ancestry

Answer 34

That our ancestry is not a direct linear progression from an ancestral hominin to Homo Sapiens.

Question 35

Where are humans originated from

Answer 35

Human origin in Africa.
5-7 million years ago, time of chimpanzee/human split, an ape ancestor began to evolve physical features that led to an upright posture.
Occurred most probably in East Africa.

Question 36

What is the oldest possibly hominin fossil

Answer 36

Sahelanthropus tchadensis
Means Sahel hominid from Chad.
Almost 7 million years old
Skull was strongly deformed by sediments
Somewhat bipedal
Foramen magnum has moved partly under the skull
Found in chad, long way from other major human fossil finds
More evidence needed before status of S. Tchadensis is confirmed
May be last common ancestor of chimpanzees and humans

Question 37

Australopithecines
What are they ?
Elaborate

Answer 37

-the southern apes
-considered first hominin fossils
-australopithecus anamensis (southern ape from the lake)
-australopithecus afarensis (southern ape from Afar) ‘Lucy’

Question 38

Who was Lucy

Answer 38

-3 million year old skeleton
-Hadar, in Afar valley in Ethiopia
-fossil had both ape like and human characteristics
-long arms short legs, as in apes
-shape of pelvis suggests bipedal
-elongated and curved fingers and toes, apes
-mixture of features suggests that it spent time in trees but could walk on the ground too
-small, about one metre tall
-ape like skull and low forehead
-protruding brow ridges
-flat face with no nose and chin
-relatively large incisors and canine teeth
-brain size about same as a modern chimpanzee
-named after Beatle’s song ‘Lucy in the sky with diamonds’
-Australopithecis afarensis
-southern ape from Afar
-Lucy would look like a bipedal ape today

Question 39

Who was “the first family”

Answer 39

-found a year after the discovery of Lucy
-site in Hadar which included over 200 fossil specimens from at least 13 individuals
-both adults and juveniles who appear to have died at the same time
-species showed sexual dimorphism
-males were much larger than the females
-A. Afarensis lived around the dry uplands of Laetoli and the wooded lake shores around Hadar about 3-4 million years ago

Question 40

What is the most widely accepted likely human ancestor

Answer 40

Australopithecus afarensis
Large number of fossils finds are available for study and timescale 3 to 3.6 million years old is about right for it to have led on to Homo

Question 41

What are Laetoli footprints

Answer 41

-Laetoli is an archeological site in Tanzania
-following a volcanic eruption about 3.5 million years ago, a group of Australopithecines walked across the mud, leaving a trail of footprints.
-discovered by Mary Leakey’s team in 1976
-oldest evidence that Australopithecines were bipedal
-bipedalism is a major milestone in human evolution

Question 42

Characteristics of Australopithecines
(Australopithecus africanus)

Answer 42

-slender gracile build
-arms longer than the legs
-curved hands and feet
-knee joints similar to humans
-walked bipedally
-flat face
-brain size larger than A.afarensis but about the same size as that of a chimpanzee
-more modern teeth than those of a.afarensis but still large compared to humans
-showed sexual dimorphism
-species lived about 3.5 - 2.5 million years ago

Question 43

Australopithecus afarensis

Answer 43

The first fossillised footprints to show evidence of bipedalism were made by this species

Question 44

Australopithecus africanus

Answer 44

A lightly built scavenger living in open woodland and the savannahs of Southern Africa around around 3-2.5 million years ago

Question 45

Paranthropus robustus

Answer 45

This species had a brain size of about 450 cm^3 with massive molars and a large jaw

Question 46

Homo habilis

Answer 46

Nicknamed the handy man, this is the oldest species known to use stone tools.

Question 47

Homo erectus

Answer 47

This species almost certainly used fire and was the first to migrate out of Africa

Question 48

Homo heidelbergensis

Answer 48

The species gave rise to homo neanderthalensis and Homo sapiens

Question 49

Divergence from australopithecines

Answer 49

Question 50

Homo neanderthalensis

Answer 50

-existed in Europe from about 200 000 years ago to about 30 000 years ago.
-thickest, muscular and robust or stocky in build and were intelligent and resourceful and lived in social communities.

Question 51

Homo sapiens are …

Answer 51

… anatomically modern humans.
We are the result of a long line biological evolution.

Question 52

Homo neanderthalensis
THE WISE MAN FROM THE NEANDER VALLEY

Answer 52

-existed in europe from about 200 000 years ago to about 30 000 years ago
-first early human fossil found in Neander valley in Germany in 1864.
-coexisted alongside fully modern humans for latter part of time
-intelligent and resourceful species
-successful for long period, surviving last ice age in Europe
-thickest, miscular, robust, stocky
-adapted to cold climate
-larger brain than modern human
-short and difficult lives (broken bones)

Question 53

How many years ago did the denisovians split from the neanderthals

Answer 53

About 350 000 years

Question 54

Summary of biological changes that have occured on human’s journey of evolution

Answer 54

-skulls have got larger as brains have increased in size. No longer have brow ridges. Upright foreheads, prominent noses and chins. Jaws and teeth have gotten smaller.

-legs increased in length. Arms shortened in proportion. Hands have less curved fingers. Fully opposable thumbs for fine manipulative movements and precision grips.

-feet have arches. Big toes are in alignment with other toes.

-pelvis rounded and spines are S shaped to support bipedal walk. Taller, less muscular & have lighter bones than neanderthals.

-brain increased in size & developed Broca’s area. Broca’s area allows for speech, which contribute to social and cultural development as a species. Larger brains give intelligence.

-intelligence enables humans to make sophisticated tools and develop modern technology. Inquisitiveness and resourcefulness enabled to spread and survive in all corners of the world. Group-living highly developed culture contiributed to success.