Human Origins and evolution
Y chromosome
-another segment of human DNA that does not undergo recombination -agreement with can hypothesis of the mtDNA results -human family is young and arose in Africa
Homo Neanderthalensis
-another species closely related to Homo Sapiens -fossils appear in Europe and the Middle East -Thicker boned than us -flatter heads than us that contained brains about the same size as, or slightly larger than ours.
The first thorough comparison of DNA molecules between humans and chimpanzees was carried out
-before the advent of DNA sequencing methods by Mary-Claire King and Allan Wilson at the University of California at Berkeley
Neanderthals disappear form the fossil record as modern humans appear
contributed to the modern human gene ppol
hemoglobin gene
under selection fore resistance to malaria
Bipedal
using only two legs for walking.
What we see when we look at genetic markers
variable a,t,g and c in human DNA is that there is indeed very little genetic differentiation by what sometime is called race
the first phase of colonization
took our ancestors through Asia and into Australia by about 50,000 years ago -not until about 15,000 years ago did the first modern humans cross from Siberia to north america to populate the new world
Multiregional Theory
which predicted that homo sapiens evolved independently in different locations throughout the old world. -2 million years for homo sapiens to have occurred
one of their methods to measure molecular differences between species relied on
-DNA-DNA bybridization -Two complemenatry strands of DNA in a double helix can be separated by heating the sample
Lucy
found in 1974 at Hadar Ethiopia, represents the next step in the evolution of hominin gait
Molecular analysis reveals that our lineage split from the chimpanzee lineage about....
- (5-7 million years ago)
our genome consists of approximately
-3 billion base pairs so 0.1% variation means that 3 million bp differ between any two people chosen at random - many of those differences are in non-coding DNA, but some fall in regions of DNA that the encode proteins and therefore influence the phenotype, so there is a fairly large reservoir of genetic variation in humans
Laetoli Tanzania
-3.5 million year old fossil footprint revealed a truly upright posture -
King and Wilson
-DNA of humans and Chimpanzees are 99 % identical has recently been confirmed by DNA sequence comparison of the human and chimpanzee genomes -Difference from humans and Chimps. one that cause a gene to be transcribed at a different stage of development -for example can have a major effect king and wilson introduced a model whereby small changes in the software could have a major impact even though the basic hardware is the same
The first hominin that left Africa is sometimes called
-Homo ergaster(early form of H.erectus and then descendant to a species the homo sapiens got it from) -Homo erectus Homo ergaster, then Homo Erectus, then Descendant species.
King and Wilson made a striking discovery
-Humans and Chimpanzee DNA differ in sequence by just 1 % -the Genomes differ by about 1 %
Bipedalism
-Lucy was bipedal (3.2 million years ago -Ardi was partially bipedal 4.4 million years ago) -also made it possible to carry material over long distances
Primates
-There are about 400 species of this, which include prosimians (lemuars, bushbabies monkeys and apes). -they all share a number of general features that distinguish them from other mammals -including nails rather than claws and eyes on front of the face instead of the side allowing stereoscopic (three dimensional vision). -most of these also have some form of opposable thumb (a thumb that can touch the finger tips of the same hand; contrast the motion of your thumb with that of your no oppossable big toe.
Mitochondrial DNA (mtDNA)
-a small circle of DNA -about 17,000 base pairs long -found in every mitochondrion -more abundant than nuclearDNA and easier to extract -its mode of inheritance -all mtDNA is inherited from your mother in the egg she produces because sperm do not contribute mitochondria to the zygote -no oppournity for generic recombination between didfferent mtDNA molecules, -the only way in which sequence variation can arise is through mutation -no genetic input from Neanderthals in modern humans
Etienne Geoffroy Saint-Hilaire
-a young organgutan on exhibit in paris looked considerably more like a human than the adult of its own species.
The divergence results into an estimate of the timing of the split between the human and chimpanzee lineage occured.....
-about 5-7 million years ago
Why did hominins become bipedal?
-bipedalism freed up our ancestors hand -human thumb as three muscles that are not present in the thumb of chimpanzees
Ardi
-capable of walking upright, using two legs on the ground but all four limbs in the trees.
Humans two closest relatives
-chimpanzees -gorillas -live only in Africa
Taxonomists
-classify all the descendants of a specified common ancestor as -belonging to a monophyletic group
Lucy Fossil
-dates from around 3.2 million years ago -member of the species Australopithecues afaraensis -much smaller than modern human -less than 4 feet tall -smaller brain -similar to humans and chimpanzees but she was bipedal
Early Hominin
-dating from about 4.4 million years ago, is a specimen of Ardipithecus ramidus from Ethiopia
Nuclear DNA
-differences between two sequence can be introduced through both mutation and recombination.
Human brain
-evolved through natural selections -evolved for mundane task like group hunting lies at the heart of much that is wonderful about humanity -ability to do things like hunt or play the piano
Neanderthals
-first appeared in the fossil record around 600,000 years ago and disappeard around 30,000 years ago. -Genetic analysis suggests that this disappearance was perhaps not as complete as the fossil record suggests.
differences in human two sources
-genetic variation -differences in environment -a person may be born with dark skin,pale, tan
Multiregional Hypothesis
-human origins because it implies that different Homo ergaster populations throughout the Old World evolved parallel -some limited gene flow among -to each produce modern H.Sapiens population - argues that our earliest hominid ancestors radiated out from Africa and Homo sapiens evolved from several different groups of Homo erectus in several places throughout the world.
first mammals
-humans (monophyletic great ape group) -blue whales -hedgehogs these were the first mammals because all three are descended from the first mammals
Humans
-humans have large brains relative to body size -large brains that have allowed our species success extraordinary technological achievement and at times destructive dominion over the planet
If the two strands are not perfectly complementary
-if there is a basepair mismatch -for example (a G paired with a T rather than a C) -less heat is required to separate the strands
Neanderthals
-if we exclude the H.floresiensis the last of the non modern humans were the this -lived in Europe and western Asia -about 30,000 years ago -sequence was strikingly different from that of modern humans -genetic analysis revealed that our ancestors did interbreed with Neanderthals and that 1% to 4% of the genome of every non-African is Neanderthal derived. -Neanderthal genomic DNA in the modern human gene pool -Neanderthal mtDNa lineage has been lost through genetic drift
Lesser apes
-include the fourteen species of gibbon -found in southeast Asia
Great Apes
-include the organgutan -gorilla -chimpanzee -strictly speaking humans
Molecular analysis
-is a powerful tool for comparing species and populations within species. -allows us to compare humans and chimpanzees and look at differences among groups of humans or groups of chimpanzees
Homo Floresiensis
-known as the hobbit -peculiar: limited to the indonesian island of flores, adults were only just over 3 feet tall -not genuinely distinct species -aberrant H.Sapiens. -distinct species derived from an archaic Homo Species (H.Erectus)
the apes are split into two groups
-lesser -great apes
Paris/juvenile ape
-looked considerably more like a human than the adult of its own species -a second human attribute is our lack of hair -a third attribute is the position of the for-amen magnum at the base of the skull -adult humans have retained the juvenile great ape foramen magnum position. -our mentality with its questioning and playfulness, is equivalent in many ways
FOXP2
-member of a larger family of evolutionary conserved genes that encode transcription factors that play important roles in development -individuals with a mutation and this thing often have difficulty with speech and language. -animals whose FOXP2 has been knocked out also have communication impairments. -plays a role in the development of many tissues -gives us a glimpse of the genetic architecture of the traits that are likely to be important in the determinationof humanness.
Studies of Mitochondrial DNA reveal that
-modern humans evolved in Africa -Allan Wilsons laboratory chose to analyze DNA sequences to reconstruct the human family tree (sequence of a segment of mitochondrial DNA from people living around the world)
people with dark skin tend to live in lower latitudes with high levels of solar radiation and people with light skin tend to live in higher latitudes with low levels of solar radiation
-pigmenation of white skin and black -a likely factor is an essential vitamin d, production of bones =can result in skeletal malformation known as rickets -the body can produce this vitamin but it needs ultraviolet radiation -natural selection favored lighter skin in the ancestors of Eurasian population because lighter skin favored the production of vitamin -hot climates where dissipating body heat is a priority a tall and skinny body form has evolved. -in colder regions natural selection favored a more robust stockier body form, as exemplified by the Inuit who have low ration of surface area to volume that promotes the retention of heat
Nenderthal DNA
-posses the modern human version of FOXP2
Allan Wilsons laboratory
-suggested that modern humans arose much more recently from Homo heidelbergensis in Africa about 200,000 years ago Aka out-of-Africa hypothesis of human origins
which is our sister group
-the chimpanzee or chimpanzees -the smaller of which is often called the bonobo
Human neoteny
-the long term evolutionary process in which the timing of development is altered so that a sexually mature organism still retains the physical characteristics of the juvenile form
amino acid
-the sequence in mice and chimpanzees whose most recent common ancestor lived about 75 million years ago, differ by a single amino acid -two amino acids are present in humans but absent in chimpanzees
selective factors?
-tool use Bipedalism permitted the evolution of manual dexterity which in turn requires a complex nervous organization if delicate hands are to be useful - social living Groups require coordination and coordination requires some form of communication and the means of integrating and acting upon the information conveyed. For example: sees group hunting as critical in the evolution of the brain: Natural selection favored those individuals who cooperated best as they pursued large prey -language. did the evolution of language drive the evolution of large brains? or did language arise as a result of having large brains? Again, we will probably never know but it is tempting to speculate that the brain and our extraordinary powers of communication evolved in concert
Rebecaa Cann Tree
-tree contained the two deepest branches-the ones that come off the tree earliest in time- are Africans -All non Africans are branches off the African tree -second the tree is remarkably shallow, that is, even the most distantly related modern humans have a relatively recent common ancestors -Cann was able to estimate the time back to the common ancestor of all modern humans as about 200,00 years
The fossil record indicated that about
2 million years ago, the hominin lineage ventured out of Africa.
Statistical analyses have shown that approximately
85 percent of total amount of genetic variation in humans occurs within a population For Example: Sweded: 8 percent occurs between population within race The characteristict we use when we assess an individuals ethnicity such as skin color, eye type and hair form are encoded by genetic variants that lie in that 7%
for the first several million years of human evolution, all the fossils form the human linage are found in
Africa -Charles Darwin
Characteristics of Primates
All primate species possess adaptations for climbing trees, as they all descended from tree-dwellers. This arboreal heritage of primates has resulted in adaptations that include, but are not limited to: 1) a rotating shoulder joint; 2) a big toe that is widely separated from the other toes and thumbs, that are widely separated from fingers (except humans), which allow for gripping branches; and 3) stereoscopic vision, two overlapping fields of vision from the eyes, which allows for the perception of depth and gauging distance. Other characteristics of primates are brains that are larger than those of most other mammals (larger brain/body ratio than similar-sized non-primates), claws that have been modified into flattened nails, typically only one offspring per pregnancy, and a trend toward holding the body upright.
The evolutionary biologist Theodosius Dobzhansky once said,
All species are unique, but humans are uniquest." Our "uniquest" status is not derived from having attributes absent in other species, but from the extent to which those attributes are developed in us.
ANATOMICAL, MOLECULAR, AND FOSSIL EVIDENCE SHOWS THAT THE HUMAN LINEAGE BRANCHES OFF THE GREAT APES TREE.
Anatomical features indicate that primates are a monophyletic group that includes prosimians, monkeys, and apes. The apes in turn include the lesser and great apes. The great apes include orangutans, gorillas, chimpanzees, and humans. Analysis of sequence differences between humans and our closest relatives, chimpanzees, indicate that our lineage split from chimpanzees 5-7 million years ago. Lucy, an unusually complete specimen of Australopithecus afarensis, demonstrates that our ancestors were bipedal by about 3.2 million years ago. Human lineage fossils occur only in Africa until about 2 million years ago, when Homo ergaster migrated out of Africa to colonize the Old World.
CULTURE IS A POTENT FORCE FOR CHANGE IN MODERN HUMANS.
Cultural evolution and biological evolution may interact, as in the case of the evolution of lactose tolerance in regions where cattle were domesticated. Other animals possess simple versions of culture, language, and even consciousness, but the capabilities of our species in all three are truly exceptional.
HUMAN HISTORY HAS HAD AN IMPORTANT IMPACT ON PATTERNS OF GENETIC VARIATION IN OUR SPECIES.
Because our ancestors left Africa very recently in evolutionary terms, there has been little chance for genetic differences to accumulate among geographically separated populations. Humans have very little genetic variation, with only about 1 in every 1000 base pairs varying among individuals. Most of the variation segregates within populations. As much as 85% of the total amount of genetic variation in humans can be found within a single population. Only about 7% of human genetic variation segregates between races. Some racial differences, such as skin color and resistance to malaria, have probably arisen via natural selection. Other racial differences have probably arisen via sexual selection.
Fossil material various
in quality and a great deal of ingenuity is often required to reconstruct the appearances and attributes of an individual from fragmentary fossil material
Explain how differences among different human populations arose by natural and sexual selection.
Differences among human populations arose by natural and sexual selection. Natural selection can be seen through the evolution of skin color, due to ultraviolet radiation and vitamin D, and body shape and size due to the ability to dissipate body heat. Sexual selection can be seen through the predominance of different facial features in different races due to humans' choice when selecting mates.
Given the high genetic similarity of humans and chimpanzees, how can we account for the differences we see between the two species?
Differences we see between humans and chimpanzees can be accounted for by differential gene expression. Basically the same genes are expressed in both organisms, but at different times and expression levels throughout development.
it would not be able to because its larynx is not capable of such subtle vocalizations.
Even if a chimpanzee wished to communicate conversationally as we do,
List three anatomical differences between chimpanzees and humans, and explain how these changes facilitated walking upright.
Four anatomical differences between chimpanzees and humans that allow humans to walk upright are: (1) the human spine is S-shaped so that weight is distributed right over the pelvis; (2) the human foot is narrower, has a more developed heel, and a larger big toe that facilitates a springier step; (3) the foramen magnum is repositioned in humans so that the skull is balanced directly on top of the vertebral column; and (4) the human pelvis is reconfigured for an upright posture with the internal organs sitting within it like a basin.
There are six major branches of primates
Lemuroidea including the lemurs of Madagascar Lorisoidea including lorises and galagos Tarsioidea with the tarsiers Ceboidea or New World monkeys Cercopithecoidea or Old World monkeys Hominoidea including apes and humans
the first humans arrived in
Madagascar only about 2000 years ago, and the colonist came from southeast asia not africa. -more variation in the African Population -non Africa population therefore began with less genetic variation .
cultural change and biological evolution is the evolution of lactose tolerance in populations for which domesticated animals became an important source of dairy product.
Most humans are lactose intolerant. Lactose, a sugar, is a major component of mammalian milk, including human breast milk. We have an enzyme, lactase, that breaks down lactose in the gut, but, typically, the enzyme is produced only in the first years of life, when we are breast-feeding. Once a child is weaned, lactase production is turned off. Lactase, however, is clearly a useful enzyme to have if there is a major dairy component to your diet.
Primates two
Our relationship to other kinds of primates is in part reflected by the pattern of similarities and differences we share with them. This pattern of similarities and differences is also used to classify different primate species into groups. There are six major branches of primates, classified as superfamilies. These include: The last three of these, hominoids, cercopithecoids and ceboids, share a common ancestor that lived sometime before 55 million years ago. These three superfamilies form a single branch, or clade, on the primate evolutionary tree.
Earliest Hominins lineage
Sahelanthropus tchadensis -discovered in chad in 2002,
24.2 PHYLOGENETIC ANALYSIS OF MITOCHONDRIAL DNA AND THE Y CHROMOSOME SHOWS THAT OUR SPECIES AROSE IN AFRICA.
Studies of mitochondrial DNA (mtDNA) suggest that the time back to the common ancestor of modern humans is about 200,000 years, implying that modern humans (Homo sapiens) arose in Africa (the out-of-Africa theory). The mtDNA out-of-Africa pattern is supported by Y-chromosome analysis, which also shows a recent African origin of modern humans. Analysis of Neanderthal DNA from 30,000-year-old material indicates that, as the ancestors of non-African humans emigrated from Africa, they interbred with the Neanderthals. Our species originated in Africa and subsequently colonized the rest of the planet, starting about 60,000 years ago.
24.3 DURING THE 5-7 MILLION YEARS SINCE THE MOST RECENT COMMON ANCESTOR OF HUMANS AND CHIMPANZEES, OUR LINEAGE ACQUIRED A NUMBER OF DISTINCTIVE FEATURES.
The development of bipedalism involved a wholesale restructuring of anatomy. Neoteny is the acquisition of sexual maturity in an otherwise juvenile state; humans are neotenous, exhibiting many traits as adults that chimpanzees exhibit as juveniles. There are many possible selective factors that explain the evolution of our large brain, including tool use, social living, and language. FOXP2, a transcription factor involved in brain development, may be important in language, as mutations in the gene that encodes FOXP2 are implicated in speech pathologies.
What do we see when we compare human and chimpanzee genomes?
The human and chimpanzee genomes help us identify genes that make us human -
Provide arguments for and against the idea that culture, language, and consciousness are uniquely human.
The idea that culture, language, and consciousness are uniquely human can be supported by the observation that humans do all three of these things to a higher level of sophistication than any other organism. However, many other organisms have simpler versions of culture, language, and consciousness, so the idea that all three are uniquely human is incorrect.
Hominins
The members of all the different species in the lineage leading to humans are called
out of Africa hypothesis
is a well-supported theory that argues that every living human being is descended from a small group in Africa, who then dispersed into the wider world displacing earlier forms such as Neanderthal.
Explain the out-of-Africa theory of human origins and how studies of mitochondrial DNA and the Y chromosome support it.
The out-of-Africa theory of human origins suggests that modern day Homo sapiens evolved from a descendant of Homo ergaster in Africa about 200,000 years ago. Mitochondrial DNA and the Y chromosome do not undergo recombination, so the only genetic variation arises from mutation. By studying the variation of these two types of genetic material from different populations of people throughout the world, scientists were able to calibrate the rate at which mutations occur build a phylogenetic tree showing the relationships between humans and that they had a common ancestor and determine the time line of modern-day Homo sapien occurrence.
Describe three possible selective factors underlying the evolution of large brains in our ancestors.
Three possible selective factors underlying the evolution of large brains in human ancestors are: (1) tool use (manual dexterity requires a complex nervous organization); (2) social living (groups require coordination, communication, and a means of integrating and acting upon the information conveyed); and (3) language (communication requires a complex nervous system).
favism, like sickle-cell anemia
is mainly a feature of populations in malarial areas or of populations whose evolutionary roots lie in these areas.
Describe what evidence suggests that chimpanzees are the closest living relatives of humans.
Using a phylogenic approach based on anatomical characteristics, scientists found that either chimpanzees or gorillas were the closest living relatives of humans. Chimpanzees were identified as being humans' closest living relatives when molecular techniques were used to compare the genetic material of chimpanzees and humans. Scientists found that our genomes differ by about 1% from that of chimpanzees.
G6PD
a gene invovled in glucose metabolism is one of several other gene implicated. People who are heterozyogotes for mutation in the g6pd gene and therefore have a g6pd enzyme deficiency can develop sever anemia when they eat certain foods most notably fava beans hence the condition is called fave beans
what factors promoted the evolution of the large human brain?
again, speculation is common, and it is unlikely we will ever have a definitive answer. Because a larger brain is metabolically expensive to produce and to maintain we can conclude that natural selection must have acted in favor of large brains.
S.tchadensis
been dated to about 7 million year ago and has a chimpanzee sized brain but hominin-type brow ridges, probably lived shortly after the split between the hominin type and chimpanzee lineages
the fossil record gives us
direct information about out evolutionary history
People who are heterozygotes
for a mutation in the G6PD gene, however, also have increased resistance to malaria, apparently because they are better at clearing infected red blood cells from their bloodstream. In areas where malaria is common, the advantage of malaria resistance offsets the disadvantage of favism.
For a full picture of human evolution, we turn to
fossils
Primates
is the name of the order of mammals to which we happen to belong. The name means 'first' or 'most important' and was given to the order by Carolus Linnaeus. While naming it that way was a matter of human ego, we can't help but feel a certain fascination with the group to which we belong. Primates typically have grasping hands (and feet) and relatively large brains. They have flatter faces than most other mammals, lacking the muzzle of dogs, bears, deer, etc. They have good vision but a more limited sense of smell than most other mammals. Most are highly social.
Langauge
occurred in Africa and through paleontologist studies of past environment, we can conclude that humans evolved in an environment similarity in man ways to today East African savanna. -the entire facial structure , in such a way that language became a possibility
Modern estimates based on comparison of many human DNA sequence indicate that
on average, about 1 in every 1000 base pairs differs among indivduals that is our level of DNA variation is 0.1% -thats about 10 times less genetic variation than in fruit flies
Hominin lineage
produced many different species in Africa, as many as 3 species living at the same time not all had common ancestors not all lead to moden humans
Grammar
provides a set of rules that allow the combination of words into a virtually infinite array of meanings. Noam Chomsky, father of modern linguistics, has pointed out that all human languages are basically similar from a grammatical viewpoint.
Rebecaa Cann
reconstructed the human family tree because of mitochondria DNA
Homo Ergaster
some hominins first left Africa about 2 million years ago. Fossils have been found throughout relatives of homo ergaster that our species, homo sapiens derived.
Teaching and imitation together make learning highly efficient.
such as ways of using tools to catch insects, that are specific to a particular population
universal grammar"
that would lead a visiting linguist from another planet to conclude that all Earth's languages are dialects of the same basic language. That universal grammar is in some way hard wired into the human brain in such a way that every human infant spontaneously strives to acquire language.
Interbreeding
the criterion that defines a species cannot be applied to fossils
