Hominin Evolution and Brain Size
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Questions and Answers

What percentage of the resting metabolic rate does a newborn use for brain function?

  • 45%
  • 65%
  • 85% (correct)
  • 95%

Why do human babies experience a relatively prolonged childhood?

  • They must learn to store fat efficiently for survival.
  • They require early independence due to resource provisioning.
  • They are born underdeveloped to pass through the mother's pelvis. (correct)
  • They need time to develop social skills.

Which statement regarding infant fat storage during development is true?

  • It decreases overall energy reserves.
  • It is unnecessary due to low metabolic demands.
  • It acts as a buffer for lean times. (correct)
  • It is detrimental to brain development.

What percentage of resting metabolic rate does a 5-year-old still utilize for brain function?

<p>45% (C)</p> Signup and view all the answers

Which of the following is a unique characteristic of human infants compared to other great apes?

<p>They have large brains relative to body size. (C)</p> Signup and view all the answers

What significant advantage did bipedalism provide to early hominids?

<p>Greater efficiency of walking (A)</p> Signup and view all the answers

Which early hominid is referred to as 'Lucy'?

<p>Australopithecus afarensis (B)</p> Signup and view all the answers

What is a consequence of the evolution of larger brain sizes relative to body size?

<p>Increased death rates due to childbirth (B)</p> Signup and view all the answers

Which factor might have influenced the selection for bipedalism among early hominids?

<p>Climate cooling and drying in Africa (C)</p> Signup and view all the answers

What unique behavior do humans demonstrate during childbirth compared to other apes?

<p>Assistance during birthing (B)</p> Signup and view all the answers

How does being bipedal affect infant birth weight in humans?

<p>Infants are born smaller than optimal for survival (D)</p> Signup and view all the answers

What is one of the primary reasons humans have a unique ability to run for long periods?

<p>Adaptive bipedalism (C)</p> Signup and view all the answers

What trade-off is presented regarding high-risk reproduction in humans?

<p>Increased risk during childbirth versus survival of the species (B)</p> Signup and view all the answers

What does the discovery of first-generation Neanderthal-Denisovan offspring indicate about hominin interactions?

<p>Mixing of Late Pleistocene hominin groups was common. (C)</p> Signup and view all the answers

Which allele is specifically mentioned as related to high altitude adaptation in modern humans?

<p>EPAS1 (C)</p> Signup and view all the answers

What remains unresolved regarding gene flow in ancient hominins?

<p>Whether gene flow occurred from modern humans into archaic hominins. (B)</p> Signup and view all the answers

How did the introgression of alleles from archaic hominins influence modern human immune systems?

<p>It introduced some beneficial immune-related alleles. (A)</p> Signup and view all the answers

What factor is indicated to have contributed to genetic adaptation in modern human populations?

<p>Gene flow from ancient hominin species. (D)</p> Signup and view all the answers

What indicates a loss of function mutation in tumor suppressor genes?

<p>Presence of mutations in both alleles (D)</p> Signup and view all the answers

What is a significant challenge posed by the evolutionary divergence of tumors in renal cell carcinoma?

<p>Therapies may ignore variations in metastases (C)</p> Signup and view all the answers

What does clonal evolution in cancer typically indicate?

<p>Development of adaptive traits in clones (D)</p> Signup and view all the answers

How does understanding the phylogenetics of pancreatic cancer challenge prior beliefs?

<p>It suggests pancreatic cancer develops more slowly than thought (C)</p> Signup and view all the answers

Which of these describes the impact of somatic evolution on organisms?

<p>It creates specific adaptations to local environments (B)</p> Signup and view all the answers

What is high-grade dysplasia?

<p>Severe precancerous tissue change (B)</p> Signup and view all the answers

What can the presence of driver mutations in tumors signify?

<p>Factors influencing tumor survival and growth (A)</p> Signup and view all the answers

Why might therapies targeting primary tumors fail against metastases?

<p>Metastases may evolve differently from the primary tumor (D)</p> Signup and view all the answers

How does the number of menstrual cycles correlate with the risk of reproductive cancers in women?

<p>The risk of reproductive cancers increases with the number of menstrual cycles. (B)</p> Signup and view all the answers

What is the primary cause of cancers related to stem cells according to evolutionary biology?

<p>Mutations that occur in stem cells. (C)</p> Signup and view all the answers

What effect does obesity have on breast cancer risk?

<p>Obesity increases breast cancer risk by releasing estrogen from fat cells. (A)</p> Signup and view all the answers

Which hypothesis suggests that lack of childhood infections leads to immune system issues in adults?

<p>The hygiene hypothesis. (A)</p> Signup and view all the answers

What role do genetic variants play in the competition among cancer cells?

<p>They enhance cancer cells' ability to compete for nutrients and evade the immune system. (C)</p> Signup and view all the answers

Why is genetic heterogeneity significant in cancer cells?

<p>It leads to an increased ability to compete for resources. (B)</p> Signup and view all the answers

What does somatic evolution being orthogonal to germline evolution imply?

<p>Evolution in somatic cells occurs independently from evolutionary changes in germline cells. (A)</p> Signup and view all the answers

What is a consequence of having significantly more menstrual cycles in postindustrial women compared to hunter-gatherer women?

<p>An increase in the risk of developing reproductive cancers. (D)</p> Signup and view all the answers

Flashcards

Infant brain growth & metabolism

Newborn brains use a high percentage (about 85%) of resting metabolic rate, decreasing to about 45% in 5-year-olds

Human infant fat storage

The selection pressure for infant fat storage during early development is significant as a buffer against lean times.

Human birth and brain size trade-off

Human babies have to be born relatively undeveloped to fit through the mother's pelvis, but this leads to an extended period for their very large brains to grow.

Overlap in juvenile stages

Humans are the only great apes who tend to have overlapping juvenile stages where those young are not yet independent.

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Implications of overlapping juveniles

The large overlap of juvenile stages in humans requires social organization for care, such as alloparenting and male provisioning of resources to allow for a longer interbirth interval for mothers.

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Early hominids

Early human ancestors, including species like Sahelanthropus and Ardipithecus, exhibiting bipedalism.

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Bipedalism

Walking on two legs, a key characteristic of hominids.

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Lucy

A famous fossil of Australopithecus afarensis, an early hominid.

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Brain size evolution

The rapid increase in brain size in hominids, compared to body size.

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Childbirth risks

High risk of death during childbirth for women, possibly a result of large brains and bipedalism in humans.

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Selection pressures

Factors affecting the survival and reproduction of organisms. Can be related to climate or foraging necessities

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Hominid characteristics

Bipedalism, evolving brain sizes over time, and high rate of reproduction are key.

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Trade-offs in evolution

Human evolution involves compromises. Big brains and bipedalism might have come at a cost of higher childbirth risk.

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Neanderthal-Denisovan Mixing

Genetic evidence suggests that Neanderthals and Denisovans interbred, producing hybrid offspring. These findings provide evidence for interbreeding between different hominin groups in the Late Pleistocene.

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Neanderthal Migrations

Neanderthals migrated between eastern and western Eurasia, as suggested by the genetic differences seen in later European Neanderthals compared to an earlier Denisovan.

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Introgression

The transfer of genetic material from one species to another through interbreeding. This is how Neanderthal and Denisovan genes have been incorporated into the modern human genome.

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Adaptive Introgression

Introgressed genes from archaic hominins that contribute to advantageous traits in modern humans. For example, the EPAS1 gene from Denisovans helps Tibetans adapt to high altitudes.

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Gene Flow from Humans to Archaic Hominins

The question of whether modern humans transferred genes to Neanderthals or Denisovans is still under investigation. There's not yet conclusive evidence to confirm or deny this.

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Cancer & Cell Division

Cancer is caused by mutations in cells, and the number of cell divisions during a lifetime can increase the risk of these mutations. Women have significantly more menstrual cycles, leading to higher breast cancer risk.

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Obesity & Breast Cancer

Obesity increases breast cancer risk because fat cells release estrogen, a hormone that influences cell growth and division.

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Hygiene Hypothesis

The idea that our clean environment might lead to weaker immune systems that overreact to harmless stimuli, increasing allergy and asthma rates.

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Old Friends Hypothesis

Our immune systems need exposure to diverse pathogens during development to function properly. Lack of this exposure might lead to overreaction to certain stimuli.

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Cancer & Somatic Mutations

Cancer often arises from mutations in stem cells, which can lead to uncontrolled cell growth. Each cell lineage has its own history of mutations, even with low mutation rates.

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Somatic Evolution

The process of mutations and natural selection within an individual's body, often leading to the development of cancers.

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Cancer Cell Competition

Cancer cells compete for resources like nutrients and evade the immune system. Cells with advantageous mutations thrive and spread.

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Cancer Cell Heterogeneity

Cancer cells within a tumor can exhibit significant genetic differences, making treating them more challenging.

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Clonal Selection

Process where cells with advantageous mutations, such as those increasing growth or resistance to therapy, are favored in a population of cells.

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Tumor Suppressor Genes

Genes that regulate cell growth and division, preventing uncontrolled cell proliferation and tumor formation. Loss of function mutations in these genes can contribute to cancer development.

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High-grade Dysplasia

Severe precancerous tissue change, characterized by abnormal cell growth and organization, indicating a high risk of developing into cancer.

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Pancreatic Cancer Phylogeny

The evolutionary history of pancreatic cancer cells, revealing that the disease can develop and persist for years before diagnosis.

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Local Adaptation (Cancer)

Cancer cells evolving to adapt to their specific location within the body, potentially making them resistant to therapies.

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Evolutionary Divergence (Cancer)

Cancer cells evolving into different lineages within a tumor, leading to variation in sensitivity to therapies.

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Therapies Miss Variation

Traditional therapies may only target specific mutations in cancer cells, failing to address the diversity of mutations within a tumor.

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Study Notes

Hominin Evolution

  • Humans are apes
  • Humans and chimpanzees share a common ancestor (7 million years ago)
  • Bipedalism is a key adaptation in hominins
  • Pelvis adaptation in humans allows for walking on two legs
  • Early hominins included Sahelanthropus (possibly bipedal 7 mya) and Ardipithecus
  • Bipedalism reduced galloping speed and tree climbing ability but increased walking efficiency
  • Climate cooling and drying in Africa pressured hominins to forage more widely (selection pressure)
  • Humans' ability to run for long periods is unusual among primates

Brain Size Evolution

  • Brain mass is significantly larger in humans compared to apes (3x larger for gorillas) relative to their body mass.
  • Brain size evolved quickly relative to body size in humans
  • Selection pressures drove brain size evolution e.g. the increased metabolic demands of a growing brain.
  • High metabolic rate in humans, compared to other primates, relative to their fat-free body mass

Childbirth and Development

  • Childbirth is risky for humans due to large brains and bipedalism
  • High risk for women in reproduction, as infants born with low birth weights face higher risk of mortality
  • Human babies are born relatively undeveloped to pass through the mother's pelvis
  • Extended childhood is an unavoidable result of human traits
  • Human brains are large and take many years to mature
  • Infants have high metabolic demands initially, with the brain using almost 85% of the RMR
  • Fat and metabolic rate is a buffer for lean times during development
  • Human offspring need extended care, leading to overlapping juvenile periods in the species, which in turn impacts social organization and interbirth interval.

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Related Documents

EVE100_F24_609-622 PDF: Human Evolution
EVE100_F24_623-660 PDF Human Evolution

Description

Explore the fascinating evolution of hominins and the significant changes in brain size that have defined human development. This quiz covers key adaptations such as bipedalism, the impact of climate on foraging, and the metabolic demands of an evolving brain. Discover how these factors have intertwined in the long journey of human evolution.

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