Natural Selection and Adaptation
Natural selection changes populations when inherited variations affect survival or reproduction. It can produce substantial adaptation to particular environments.
The Investigative Question
What can natural selection accomplish when useful heritable variation is available?
What We Observe
Populations contain heritable differences. When some differences affect reproductive success, their frequencies can change over generations.
Scientific Background
Natural selection does not create every variation upon which it acts. Mutation, recombination, gene flow, and other processes generate or redistribute variation. Selection changes the representation of variants according to their effects in particular environments.
Why It Matters
Natural selection is central to evolutionary theory, but selection must be considered together with the origin of the variations being selected.
What Is Known
Natural selection has been observed in laboratory and natural populations. It can produce measurable adaptation, including changes in physiology, morphology, behavior, and resistance to environmental challenges.
What Is Proposed
Evolutionary theory proposes that repeated selection acting upon heritable variation can contribute to larger biological changes over long periods.
What Remains Uncertain
The contribution of selection to a particular ancient innovation depends upon reconstructing the relevant variations, functions, environments, and historical sequence.
Design Relevance
Intelligent Design accepts that natural selection can preserve and amplify advantageous variation. The investigative question is whether selection acting upon available variation is sufficient to account for the major innovations under consideration.
Assessment
Natural selection is a demonstrated mechanism of adaptation. Questions concerning major innovation require us to examine both the power of selection and the origin of the functional variation upon which it acts.