Capsules

Muscle Contraction

Muscle shortens because two sets of protein filaments slide past one another, driven by myosin heads that repeatedly attach to actin, pivot, and let…

The Major Transitions in Evolution

The proposal that the history of life is punctuated by a small number of events in which independently reproducing entities combined into a larger…

The Sexy Son Hypothesis

The proposal that a female may benefit from choosing an attractive mate even if he provides nothing else, because her sons inherit the attractiveness…

The Baldwin Effect

The proposal that behaviours learned during life can steer subsequent genetic evolution, without any Lamarckian inheritance of acquired traits. It…

The Cell Cycle

The ordered sequence a cell follows to duplicate itself, controlled by checkpoints that stop it proceeding until the previous stage is complete.…

Group Selection

The proposal that natural selection can act on groups as well as individuals, favouring traits that benefit the group at the individual's expense. It…

Niche Construction

The proposal that organisms do not merely adapt to environments but build them, and that the environments they build become selection pressures for…

The Extended Evolutionary Synthesis

The proposal that evolutionary theory needs restructuring to give causal roles to development, inheritance beyond genes, and organisms shaping their…

The Red Queen Hypothesis

The proposal that organisms must keep evolving simply to maintain their position, because everything they interact with is evolving too. It takes its…

Antagonistic Pleiotropy

The proposal that ageing is caused by genes which help early in life and harm later, and which selection favours anyway because early effects matter…

The Disposable Soma Theory

The proposal that organisms age because it is not worth the energy to maintain a body indefinitely when something will kill it anyway. It explains…

The Free Radical Theory of Ageing

The proposal that ageing is cumulative damage from reactive oxygen species produced by normal metabolism. It dominated ageing research for half a…

Nitrogen Fixation

Air is nearly eighty percent nitrogen and almost nothing can use it. Breaking the bond that holds the molecule together is what makes proteins and…

Apoptosis

Cells kill themselves on instruction, following a controlled programme that dismantles them tidily. It builds bodies by removing what is not needed,…

The Drunken Monkey Hypothesis

The proposal that the human attraction to alcohol descends from a primate ancestor's taste for fermenting fruit, in which ethanol signalled ripeness…

Circadian Rhythms

Almost every organism runs an internal clock with a period of about a day, generated by a molecular feedback loop inside individual cells. It runs…

Viral Eukaryogenesis

The proposal that the cell nucleus originated as a large DNA virus that took up permanent residence in an ancestral cell. It is a minority position…

Osmosis

Water moves across a membrane from where solutes are dilute to where they are concentrated. It requires no pump and no energy input, it generates…

Meiosis

The cell division that halves the chromosome number and shuffles the genome at the same time. It is the reason sexual reproduction produces…