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HOT (Human Origins Today) Topic: The Earliest Human Ancestors

Smithsonian's National Museum of Natural History・39 minutes read

Dr. Ashley Hammond and Briana Pobiner discuss early human ancestors and locomotor evolution, highlighting key species and factors influencing bipedalism through fossil remains and research in Africa. Continued paleontological work in Africa is crucial to fill gaps in understanding hominin origins, with upcoming fieldwork in Southern Kenya offering potential to transform knowledge with six million-year-old fossils.

Insights

  • Bipedal locomotion is a crucial feature that distinguishes hominins from other species, impacting various anatomical aspects such as knee positioning, pelvis structure, foot anatomy, and spinal curvature. This adaptation was likely influenced by factors like climate change and the necessity to cover longer distances in search of food, setting hominins on a unique evolutionary path.
  • Filling gaps in the fossil record through continued paleontological work in Africa is essential for enhancing our knowledge of hominin origins, as the absence of fossil apes from equatorial Africa poses a significant challenge. Understanding the evolution of bipedalism and differentiating between hominin and ape species in the fossil record relies on meticulous fieldwork, nuanced anatomical analysis, and the collaboration of experts across disciplines.

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Recent questions

  • What is the significance of bipedality in hominins?

    Bipedality is a defining feature of hominins, crucial for locomotion and evolutionary development. It involves knee positioning, pelvis reorganization, foot structure, and vertebral column curvature.

  • What factors influenced the evolution of bipedalism in early hominins?

    The evolution of bipedalism in early hominins is theorized to be influenced by a combination of factors, including climate change and the need to travel longer distances for food.

  • What are some early hominin contenders in the fossil record?

    Early hominin contenders include Sahelanthropus from Chad, Orrorin from Kenya, and Ardipithecus from Ethiopia, each showing evidence of bipedality through skeletal remains.

  • How does the anatomy of early hominins differ from modern humans?

    The anatomy of early hominins remains largely unknown due to gaps in the fossil record, but differentiation between hominin or ape genus and species depends on radical differences in remains.

  • Why is continued paleontological work in Africa crucial for understanding hominin origins?

    Continued paleontological work in Africa is crucial for filling gaps in knowledge about hominin origins, as the lack of fossil records in equatorial Africa hinders understanding and differentiation between hominin and ape species.

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Summary

00:00

Early Human Ancestors: Evolution of Bipedalism

  • Briana Pobiner, a paleoanthropologist and educator at the Smithsonian's National Museum of Natural History, hosts a program on The Earliest Human Ancestors as part of the Hot Topic series.
  • The discussion offers closed captioning, and questions can be submitted via the Q&A box on the Zoom interface.
  • Dr. Ashley Hammond, Assistant Curator of Biological Anthropology at the American Museum of Natural History, presents on the evolution of locomotor behaviors in East Africa.
  • Dr. Hammond's research focuses on bipedal locomotion and the postcranium, particularly the pelvis, as an indicator of locomotor evolution.
  • Collaborating with researchers from the National Museums of Kenya, Dr. Hammond conducts paleontological research in hominin-bearing deposits in Kenya.
  • The hominoid superfamily includes lesser apes, great apes, and humans, with hominins being species more closely related to humans than chimpanzees.
  • Canine reduction and habitual bipedality are defining features of hominins, with bipedality being crucial for locomotion and setting hominins on their unique evolutionary path.
  • Features associated with bipedality include knee positioning, pelvis reorganization, foot structure, and vertebral column curvature.
  • The evolution of bipedalism in early hominins is theorized to be influenced by a combination of factors, including climate change and the need to travel longer distances for food.
  • Early hominin contenders include Sahelanthropus from Chad, Orrorin from Kenya, and Ardipithecus from Ethiopia, with each species showing evidence of bipedality through skeletal remains.

15:39

Hominin Origins: Fossil Record Gaps and Challenges

  • Australopithecus is followed by genus Homo in the hominin fossil record.
  • The bulk of hominin fossils come from the Pliocene and Pleistocene periods.
  • The Miocene period was rich in fossil ape species, with over a hundred species.
  • Fossil apes' locomotor behaviors varied greatly, unlike living hominoids.
  • Understanding hominin origins requires considering fossil apes.
  • The lack of fossil apes from the latest Miocene in Africa poses a challenge.
  • Modern apes are concentrated around the equator, unlike fossil apes that were more widespread.
  • The absence of fossil records in equatorial Africa hinders understanding of hominin origins.
  • The anatomy of early hominins remains largely unknown due to gaps in the fossil record.
  • Continued paleontological work in Africa is crucial for filling gaps in knowledge about hominin origins.

32:54

Hominin Fossil Record: Genus and Species

  • Differentiation between hominin or ape genus and species in the fossil record depends on the radical differences in remains.
  • Similar remains to existing species are likely placed within an existing genus.
  • Nuanced characters in remains lead to allocation as a new species, especially with multiple individuals.
  • Fieldwork for fossil searching relies on word of mouth and confirmation of deposit age and nature by a geologist.
  • Stable isotope studies indicate increasing aridity in Africa, supporting the Savannah hypothesis.
  • Confidence in hominin fossil landscape sampling is high in Eastern and Southern Africa but low in Western and Northern Africa.
  • Ardipithecus ramidus shows bipedal adaptations in arboreal environments, suggesting bipedality in trees.
  • Genomic methods are limited in older fossils, but proteomics offers potential for older samples.
  • Sahelanthropus may be an early hominin based on upright posturing, but more data is needed for confirmation.
  • Development of early hominin brains resembled ape-like patterns, differing from modern humans.

50:14

Hominin Evolution: Joints, Bipedalism, and Fossils

  • Nariokotome Boy, a 1.5 million year old Homo erectus from Kenya, had smaller joints compared to modern humans.
  • The shape of joints changed from elongate in early hominins to squat and broad in later hominins.
  • Australopithecus marks a period of heavy diversification in hominin evolution.
  • The possibility of finding a missing link between fossilized apes and pre-Homo species is uncertain.
  • Bipedalism may have arisen from climate change, but modern apes are highly specialized for their environments.
  • The fossil record gap in equatorial Africa may be due to the lack of suitable conditions for fossil preservation.
  • Excitement for upcoming fieldwork in Southern Kenya, where six million-year-old fossils could transform understanding of hominin origins.
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