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DOWN’S SYNDROME IN NEANDERTHALS

4th July, 2024 Health

DOWN’S SYNDROME IN NEANDERTHALS

Source: Earth.com

Disclaimer: Copyright infringement not intended.

Context

  • Recent research has documented the first-ever case of Down syndrome in Neanderthals.
  • This discovery not only adds a new dimension to our understanding of Neanderthal genetics but also suggests that these prehistoric humans exhibited altruistic behaviors, indicating their capacity for empathy and community care.

Details

Down Syndrome

  • Down syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of an extra copy of chromosome 21.
  • This extra genetic material affects development and causes the characteristic features associated with the syndrome.

History

  • 1866: John Langdon Down, a British physician, first described Down syndrome as a distinct form of intellectual disability.
  • 1959: Jérôme Lejeune, a French geneticist, discovered that Down syndrome was caused by trisomy 21.

Genetics

  • Chromosome 21: Normally, humans have 23 pairs of chromosomes. Down syndrome occurs when there is an extra copy of chromosome 21.
  • Types:
    • Trisomy 21: Most common type (about 95% of cases), caused by nondisjunction during cell division.
    • Translocation Down Syndrome: Occurs when part of chromosome 21 becomes attached to another chromosome.
    • Mosaic Down Syndrome: Some cells have an extra copy of chromosome 21, while others do not.

Prevalence

  • Occurs in approximately 1 in 700 live births worldwide.
  • Risk increases with maternal age, particularly after age 35.

Characteristics

  • Physical: Flattened facial features, almond-shaped eyes, short neck, small ears, and a single crease across the palm.
  • Cognitive: Intellectual disability, ranging from mild to moderate.
  • Health: Increased risk for congenital heart defects, respiratory issues, hearing problems, and thyroid conditions.

Neanderthals

  • Neanderthals, Homo neanderthalensis, are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago.
  • They are closely related to modern humans, sharing a common ancestor approximately 400,000 to 500,000 years ago.

History

  • 1856: First recognized Neanderthal fossils discovered in the Neander Valley, Germany.
  • Name: Derived from the location of the first discovery (Neander Valley).
  • Origins: Evolved from Homo heidelbergensis in Europe and parts of western Asia.
  • Timeline: Existed from around 400,000 to 40,000 years ago.
  • Relation to Modern Humans: Shared a common ancestor with Homo sapiens about 400,000 to 500,000 years ago.
  • Fossil Sites: Numerous significant fossil sites across Europe and Asia, including La Chapelle-aux-Saints, Shanidar Cave, and Vindija Cave.

Physical Characteristics

  • Cranial Features: Larger cranial capacity (average 1500 cm³), elongated skull, prominent brow ridges, and lack of a chin.
  • Postcranial Anatomy: Robust and muscular build, shorter limbs compared to modern humans, adaptations for cold climates.
  • DNA Evidence: Interbred with modern humans, contributing 1-2% of DNA in non-African modern human populations.

Habitat and Distribution

  • Geographical Range: Lived in Europe, Western Asia, and the Middle East.
  • Habitat: Adapted to a range of environments from cold glacial regions to temperate climates.

Tools and Technology

  • Mousterian Tools: Associated with the Middle Paleolithic period, characterized by flake tools and scrapers.
  • Innovations: Use of fire, construction of shelters, and creation of clothing from animal hides.

Culture and Behavior

  • Diet: Primarily meat-based, but also consumed plant materials. Evidence of hunting large game.
  • Burial Practices: Evidence of intentional burials, sometimes with grave goods, indicating possible ritualistic behaviors.
  • Art and Symbolism: Limited but significant evidence of symbolic behavior, such as cave art and personal ornaments.

Cognitive Abilities

  • Brain Structure: Larger brains than modern humans, with different structural organization.
  • Social Structure: Evidence of social care, group hunting, and possibly complex social interactions.
  • Language: Likely capable of some form of speech, based on anatomical evidence (e.g., the hyoid bone).

Interaction with Modern Humans

  • Interbreeding: Genetic evidence shows interbreeding between Neanderthals and modern humans.
  • Competition and Cooperation: Likely both competed for resources and interacted with modern humans.

Extinction

  • Timing: Disappeared around 40,000 years ago.
  • Causes: Likely a combination of factors including climate change, competition with modern humans, and possible assimilation into Homo sapiens populations.

Sources:

Earth.com

PRACTICE QUESTION

Q: With reference to Down's syndrome, consider the following statements:

  1. Down's syndrome is caused by the presence of an extra copy of chromosome 21.
  2. Individuals with Down's syndrome often exhibit intellectual disability and characteristic facial features.
  3. The risk of having a child with Down's syndrome increases with the mother's age.

Which of the statements given above is/are correct?

a) 1 and 2 only
b) 1 and 3 only
c) 2 and 3 only
d) 1, 2, and 3

Answer: d)