Inquisitive Chapter 19: Human Evolution
Recent studies have provided a substantial amount of information about the presence of Neanderthal genome in modern human populations. How much of the Neanderthal genome can found in the human population?
20-30% in non-African humans
One catalyst that led to the rise of the hominin lineage was a change in the ecology of the __________ that occurred about ___________ ago. Large expanses of the __________shifted from _____________ to ______________. The ______________lineages remained in the_______ while Hominina moved to the ___________
African tropics that occurred about 6 million years ago. Large expanses of the African continent shifted from tropical forest to savannah. The chimpanzee and gorilla lineages remained in the tropical forest while Hominina moved to the savannah
Why is there still debate about hominin classification?
All species in the clade are extinct except for humans, and there are a limited number of specimens, making it difficult to determine species boundaries from fossil evidence.
The understanding of hominoid phylogeny has been somewhat in flux as new fossil discoveries are uncovered and increasing sophistication of molecular techniques continues to enhance our ability to extract and analyze DNA. Currently, the subtribe Hominina includes ____.
Correct members of the genus Homo, living and extinct archaic hominin genera Incorrect only living members of the genus Homo; members of the genus Pan
Sahelanthropus tchadensis was discovered in Chad in 2001 by Brunet et al. It is an example of the difficulty researchers encounter when attempting to classify a species as being definitively in the hominin lineage at this point in geologic history. Why are fossils from this time period so difficult to definitively place?
Correct :This is the time period right after the split of chimpanzees and hominins, so it is difficult to place species based on morphological characters. Fossils tend to be in poorer condition than others in hominin lineage because of relatively great age. Incorrect: We do not have technology that is advanced enough to provide accurate reconstruction, so morphological characters are somewhat ambiguous. Large areas of Africa are not accessible to researchers due to political and social upheaval, limiting the number of fossils collected.
Page 69619.3. The Emergence of Anatomically Modern Humans Homo sapiens lived in some of the same geographic areas of Europe and central Asia as other Homo species, including H. neanderthalensis. Although physically distinct from H. sapiens, there is evidence the two species interbred and shared numerous social and cultural characteristics. What social and cultural characteristics did the two species share?
Correct Answers: cooked with fire cared for sick, injured, and elderly capable of speech made elaborate mode 3 tools and hunted large game Incorrect Answers: created elaborate structures for shelter produced art and musical instruments
Determining the geographic origin of the great apes has been challenging, as fossils are sparse from the time of the divergence (14 million years ago) until about 5 million years ago. What are the two predominant hypotheses currently being investigated?
Correct: Eurasian origin , East African origin Incorrect: Western European origin, Middle Eastern origin
Why would the evolutionary history of laterally transmitted pathogens not mirror the evolutionary history of their hosts?
Correct: Lateral transmission can occur from one population to another in a single migration event. Lateral transmission is from one person to an unrelated individual. Laterally transmitted pathogens can move back and forth between humans and non-human reservoirs. Incorrect : Laterally transmitted pathogens move from parents to offspring.
How does this model partially support the multiregional hypothesis and how does that dispute what scientists believed two decades ago about hominin history?
Different populations of modern humans inherited genetic material from different sources as predicted. This disputes what scientists previously believed, that other hominins were rapidly outcompeted by H. sapiens and disappeared.
The graph on the left illustrates human genetic variation and population distance from Addis Ababa. The graph on the right indicates genetic variation in Helicobacter pylori and population distance from East Africa. What do these results indicate that humans and H. pylori have in common?
For both, genetic diversity decreased with distance from Africa, which suggest an African origin and global migration.
Which statement accurately describes the development of the gorilla, chimp and human lineages?
Gorillas split from the human/chimpanzee lineage, humans and chimpanzees split shortly thereafter.
According to the out-of-Africa model, which statement accurately reflects the approximate hominin lineage that ultimately led to modern humans, Homo sapiens?
Homo ergaster arises in Africa and gives rise to Homo heidelbergensis. H. heidelbergensis gives rise to one branch that leads to Neanderthals and Denisovans and one branch that leads to H. sapiens.
The serial founder effect describes the process where a subset of a population migrates into a new area, resulting in a loss of genetic diversity in the newly established population. This process can continue as a group from the newly established population then migrates to a new area to establish a new population, further reducing genetic diversity. After examining this graph, place the geographic regions in the order of likely establishment from the earliest founding human population.
Middle East, East Asia , Oceania, Americas
Consider what we know about the migration of hominins out of Africa and the coexistence of H. sapiens, H. neanderthalensis, and Denisovans in Eurasia. What would be a reasonable prediction about the presence or absence of Neanderthal DNA in the genomes of humans descended from Africans and humans descended from Europeans and Asians?
Neanderthal DNA should be found in humans descended from non-Africans.
Fossils of Proconsul indicate they were closely related to the common ancestor of all living apes, but it is anatomically different from extant ape species. What is the primary characteristic that distinguishes them from extant apes?
Proconsul lacked the limb mobility that characterizes extant apes.
The Tibetan people typically carry a variant allele that contributes to their high altitude tolerance. Researchers discovered this allele was rare in the closely related Han Chinese which led them to question the history of the allele. Ultimately, it was determined that __________.
The haplotype was introduced by interbreeding with Denisovan hominins.
What does this revised model of gene flow between Neanderthals, Denisovans, and modern humans indicate about the genetic distance between these three groups?
The three groups are not equidistant. Denisovans have a significantly greater genetic distance from modern humans than Neanderthals.
Hominins learned how to control and utilize fire in ways that may have shaped the course of hominin evolution. Anthropologist Richard Wrangham hypothesized a connection between fire use and morphological changes that occurred in the hominin lineage leading to modern humans. What was this hypothesis?
The use of fire to cook food (as opposed to eating raw food) provided large energetic stores that are easily consumed and processed; this reduced nutritional challenge and resulted in distinct morphological changes including a large increase in brain size.
What is the primary distinction between the multiregional hypothesis and the out of Africa hypothesis?
There are differing fates for premodern hominin lineages in Europe and Asia.
Studies of mtDNA indicated there is substantially more mtDNA diversity within Africa than across the rest of the globe, and the coalescence time for human mtDNA is between 120-230,000 years ago. What did this tell researchers about the geographic emergence of Homo sapiens?
This dates to the possible time of emergence of H. sapiens in Africa.
Researchers have long questioned how hominins transitioned from premodern hominins to modern hominins, and when and where that took place. The multiregional model suggests that hominins left Africa and colonized the Old World a single time as Homo ergaster. Click on the graph that represents this hypothesis.
This graph does illustrate the multiregional hypothesis, which suggests that after leaving Africa, H. ergaster populations diverged modestly, but did not undergo speciation because of modest gene flow between the populations. These populations then evolved into Homo heidelbergensis and then Homo sapiens.
Research by Kann et al. used restriction mapping to create a phylogenetic tree based on mtDNA. Their study was followed by Ingman et al., whose results supported Kann's findings. If Ingman's results indicated greater mitochondrial diversity in non-African mtDNA, how would this have supported or disputed Kann et al.'s findings?
This would have disputed Kann et al.'s findings as their results indicated greater mtDNA diversity within Africa than in the rest of the world combined.
What is the primary difference seen between the Y chromosome and mtDNA in terms of diversification and effective population size?
Y chromosome effective population size and diversification increased and then experienced a significant bottleneck after the migration out of Africa but the mtDNA did not.
You are working as a cultural anthropologist and a paleontologist colleague working in Europe has discovered a set of hominin fossils deep in a cave that are relatively undisturbed. She has asked you to help verify her species identification and has sent you detailed images of the fossils. The skull of one fossil has a pronounced brow ridge with larger eyes and a protruding jaw. In another chamber of the cave, a buried skeleton is lying in a manner that indicates its final position was carefully arranged. The hands are folded on the chest with the remains of a wooden flute. The fossils of both skeletons have been dated to be approximately 35,000 years old. How do you explain your colleague's findings?
Your friend has likely discovered the remains of both H. neanderthalensis and H. sapiens which coexisted and interbred in areas of Europe.
On a timescale of days to weeks, humans undergo _______capacity, which includes physiological changes such as an _________. On a developmental timescale, humans exhibit _______, with humans reared at higher altitudes having a higher ________. On an evolutionary timescale, a high-altitude population will evolve genetic adaptations that help them function in_______conditions. The Tibetans have undergone_________ as a result of living in their environment.
acclimatization; increase in red blood cells ;phenotypic plasticity ;aerobic capacity ; low oxygen ;genetic adaptations
Darwin and Huxley used phenotypic characters to infer that humans are hominoids, which makes us members of the superfamily Hominoidea, a group of species informally grouped together as the apes. Although fairly controversial at the time (1863), modern genetic sequence data definitely confirmed this relationship over 140 years later. However, humans are more closely related to some apes than others. Please order these groups from most closely related to humans to least closely related to humans.
bonobo/chimpanzee gorilla orangutan gibbon
Which skull characteristics distinguish the robust australopithecans from other hominins?
correct : large teeth distinctive top ridge broad, protruding cheek bones incorrect: large brain size
Advancements in the application of molecular technologies has continued to lead to more insights about human evolution and patterns of migration. Lie et al. (2008) used 650,000 SNPs (single nucleotide polymorphisms) to analyze clustering of 938 humans from around the world. What do their results tell us about human migration?
correct :The phylogeny indicates strong geographic structure. The root of the tree is in Africa, which supports the out-of-Africa hypothesis. incorrect :The phylogeny indicates that modern humans originated in Asia based on the large cluster of diversity. Although the tree is rooted in Africa, it does not clarify the order of expansion in to the Middle East, Europe, Central Asia and East Asia.
The archaic hominin lineage that eventually leads to modern humans are primarily represented by members of the genus _____.
correct: Australopithecus incorrect: Paranthropus Ardipithecus Sahelanthropus
Scientists' understanding of what distinguishes the hominin lineage has changed as research on hominins and other species gives us a better understanding of our own lineage and others. Which are the characteristics that distinguish the hominin lineage?
correct: changes in dentition skeletal changes that facilitated bipedal locomotion size of the braincase Incorrect: use of tools development of language
A number of hypotheses have been proposed to explain why bipedalism was favored in the Hominina lineage. What are they?
correct:Standing upright helped keep hominins cool in direct sunlight. Bipedalism frees up hands for carrying items and plucking fruit. Bipedalism is more energetically efficient than knuckle walking. incorrect :Bipedalism enabled hominins to outrun their predators.