DOWN’S SYNDROME IN NEANDERTHALS

Source: Earth.com

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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: Down's syndrome is caused by the presence of an extra copy of chromosome 21. Individuals with Down's syndrome often exhibit intellectual disability and characteristic facial features. 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)