Life in the UniverseAnswer
How do astronomers find planets around other stars?
Distant worlds can reveal themselves through changes in starlight and the motion of their stars.
THE QUESTION LIBRARY LIFE IN THE UNIVERSE
Does evolution have a goal or a direction?
THE SHORT ANSWER
Evolution has no built-in destination. Traits can change directionally, remain outwardly similar, or lose an ancestral role while retaining a function.
WHERE THE EVIDENCE STANDS
How sure are we?
- Evolution plans ahead toward a predetermined destination.
- Similar outward appearance means evolutionary change has stopped.
- A vestigial structure can retain a current function.
Evolution has no built-in destination or ability to plan ahead. It can nevertheless show directional change. The distinction is between a pattern we observe and a future goal.
THE LONG ANSWER
THE LONG ANSWER · ABOUT 2 MINUTES
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God Plays Dice answers big questions in plain words, with sources and one of six honest labels.
Sources & further reading
(5)
- Evolution Resources ↗National AcademiesDefinitions; FAQs.
- Biology 2e: Adaptive Evolution ↗OpenStax, Rice UniversityStabilizing selection; directional selection; existing variation.
- The African coelacanth genome provides insights into tetrapod evolution ↗Amemiya and colleagues, Nature 496:311–316 (2013)The slowly evolving coelacanth.
- Sexual selection targets cetacean pelvic bones ↗Dines and colleagues, Evolution 68:3296–3306 (2014)Abstract; anatomy.
- Biology 2e: Chordates ↗OpenStax, Rice UniversityPost-anal tail.
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CONTINUE THE THREAD
Where this question leads.
Life in the UniverseAnswer
Could a planet without a star support life?
A world with no sunrise could still have internal heat. The question is whether it can keep water liquid and supply usable energy.
Life in the UniverseAnswer
How can identical twins with the same DNA turn out so different?
Identical twins develop from one fertilized egg and begin with almost the same DNA. Yet their conditions before birth, later environments and gene activity can differ. Shared DNA…