Understanding Cousins and Genetic Relationships

Concept of Cousins

• Cousins: Relatives who share a common ancestor but are not direct descendants of each other
• Important to determine the degree and the removal

Family Tree and Generations

• You (the individual): Born from your parents
  • Share 50% DNA with mom and dad
• Children: Created from your DNA (50% from each parent)
• Grandchildren: Children of your children
• Great Grandchildren: Children of your grandchildren
• Parents: Directly above you in the family tree
• Grandparents: Parents of your parents
• Great Grandparents: Parents of your grandparents

Siblings

• Siblings: Share same parents, same generation level
• Nieces/Nephews: Children of your siblings (can be referred to as 'niblings')
  • Grand Niblings: Children of your niblings
  • Great Grand Niblings: Children of your grand niblings

Aunts and Uncles

• Aunts/Uncles: Siblings of your parents
• Grand Aunts/Uncles: Siblings of your grandparents
• Great Grand Aunts/Uncles: Siblings of your great grandparents

Determining Cousins

• Common Ancestors: Ancestor from whom two people are directly descended
  • Criteria: Pass through no generations to be a direct relative
• Degree and Removal:
  • Degree: Number of generations to the common ancestor (smallest number) determines the cousin degree
  • Removal: Difference in the number of generations between the two people and the common ancestor

Examples of Cousin Relationships

• First Cousins: Share grandparents
  • Pass through 1 generation each to common ancestor
  • Example: Children of aunts/uncles
• First Cousins Once Removed: Your first cousins' children
  • You pass through 1 generation, they pass through 2 (1+1)
  • Differs by 1 generation
• Second Cousins: Share great grandparents
  • Both pass through 2 generations
  • Example: Grandchildren of your grandparents' siblings
• Second Cousins Once Removed: Your second cousins' children
  • You pass through 2 generations, they go through 3 generations
  • Differs by 1 generation

Genetic Similarity

• Proportion of Shared DNA:
  • Children/Siblings: 50% shared DNA
  • Aunts/Uncles: 25% shared DNA
  • First Cousins: Approx. 12.5% shared DNA (7-14%)
  • First Cousins Once Removed: Approx. 6% shared DNA
  • General Rule: DNA halved every generation

Fun Facts

• Siblings can be considered 0th cousins
• You are your own 0th cousin, but the 'negative cousins' concept doesn’t hold ground unless we consider generational movement downward
• Overall, all humans share over 99% of their DNA
• Larger perspective: All beings and matter originated from the Big Bang

Summary

• Understanding relationships through common ancestors
• Degrees and removals as metrics for cousin relationships
• Explaining genetic similarities helps in understanding family ties

Key Takeaway: All beings on Earth and beyond are interconnected through the vast history of the universe.