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Human Evolution and Ecology - Week 11 Lecture Notes

Topic = The Hominid Progression (continued) and the Modern Humans and Recent Evolution

1. Overview of Modern Humans and Recent Evolution

  • This section provides a comprehensive discussion of the hominid progression leading to modern humans and the recent evolutionary changes observed in human lineage.

2. News Updates and Fossil Discoveries

  • Dragon Man Skull Discovery

    • The recent finding of the 'Dragon Man' skull raises questions about its classification as a possible new human species.

    • The cranium combines both ancient and modern features, which contributes to ongoing debates surrounding human origins.

    • The skull was discovered hidden down a well and provides crucial information regarding human evolution that does not align with previously established narratives.

    • Source: National Geographic, Maya Wei-Haas.

  • Ancient DNA Insights on Denisovans

    • A YouTube video discusses the discovery of ancient DNA indicating that the 'Dragon Man' is related to the Denisovan lineage.

  • Oldest Hominin Footprints

    • In a study published in 2021, scientists reported footprints found in Crete as possibly the oldest hominin footprints ever found, dated to 2017.

3. Divergence of Great Apes and Hominins

  • The evolution and divergence of the human lineage from great apes began over 5 million years ago:

    • Three significant transitions in human evolution:

    • First Transition (Locomotion) - Changes in locomotion showcased in anatomical fossil records.

    • Second Transition (Dentition) - Changes in tooth structure correlating with dietary shifts.

    • Third Transition - Developmental transitions that are a result of natural selection across different ecological conditions.

  • The evidence of changes between various hominid fossils shows differences in size, shape, and functional adaptations.

4. Major Hominin Candidates

  • Early Hominid Candidates

    • Sahelanthropus tchadensis (7.0 – 6.0 million years ago, MYA)

    • Pronunciation: Sa_helanthropus chadensis

    • Likely bipedalism based on cranial and dental morphology despite having a small brain size similar to that of chimpanzees (estimated between 320 cc – 380 cc).

    • Notable finding includes a mostly complete cranium.

    • Orrorin tugenensis (6.0 MYA)

    • Pronunciation: Orrorin tugen_ensis

    • Significance lies in the fossil correlation between morphology and bipedal walking.

5. Fossil Evidence and Sites

  • Fossil sites relevant to early hominins include:

    • Toros-Menalla, Chad (7.0-5.2 MYA)

    • Tugen Hills, Kenya (6.0 MYA)

    • Middle Awash, Ethiopia (5.8-5.2 MYA, Ardipithecus kadabba)

    • Lothagam, Kenya (5.8 MYA)

    • Aramis, Ethiopia (4.4 MYA, Ardipithecus ramidus)

6. Australopithecus and Related Species (4.2-1.0 MYA)

  • Characteristics of Australopithecus

    • Small-bodied, small-brained, and modestly prognathic-faced bipedal apes.

    • Key species and timeframes include:

    • Australopithecus anamensis (4.2 – 3.9 MYA)

    • Australopithecus afarensis (3.9 – 2.9 MYA)

      • Notable for the discovery of Lucy, a model representative of this species.

    • Australopithecus africanus (3.5 - 2.0 MYA)

      • Found in South African cave deposits.

      • Initially described as a gracile hominid due to its lighter body and smaller jaws.

    • Robust Australopithecines

      • Specialized for hard-object diets with significant musculature adaptations seen in their skull morphology.

      • Includes species such as Americanus boisei (2.3 - 1.2 MYA) and Australopithecus robustus.

7. Homo Evolution

  • Transition towards the genus Homo about 2.4 MYA:

    • Homo habilis: Early representatives included KNM-ER specimens showing variable brain sizes and physical characteristics associated with early tool use (Oldowan tools).

    • Homo erectus: Marked a significant progression in hominid development around 1.9 MYA with notable changes including larger body sizes and brain capacities, adaptations for long-distance travel, and out-of-Africa migration.

8. Neanderthals and Modern Humans (Homo sapiens)

  • Neanderthal features include:

    • Large brains, robust skeletal structure, and distinct cranial morphology.

    • Evidence for communal living and sophisticated tool use.

    • Possible implications of care within Neanderthal communities due to evidence of healed injuries seen in fossils.

  • Morphological Contrasts with Homo sapiens:

    • Homo sapiens display a distinct evolutionary advantage in anatomical structure and behavioral complexity.

9. Modern Human Behavior and Genetic Studies

  • Fossil evidence and genetic data indicate that Homo sapiens evolved about 100,000 – 200,000 years ago in Africa and underwent migrations outwards, interbreeding with other Homo species including Neanderthals and Denisovans.

  • This complex backdrop of evolutionary history showcases how modern humans, with advancements in technology and culture, navigated their environments and established diverse populations across the globe.

10. Out of Africa Model

  • Population genetics illustrate the dispersal of modern humans from Africa, with waves of migration occurring around 60,000 years ago, leading to genetic intermingling with local populations, influencing traits seen in present-day human beings.

Conclusion

  • The chronicle of human evolution is characterized by significant fossil discoveries, genetic studies, and the continual reassessment of anthropological data, prominently leading to a deeper understanding of humanity’s origins.