Production of new individuals along a leaf margin of the miracle leaf plant (Kalanchoe pinnata). The small plant in front is about 1 cm (0.4 in) tall. The concept of "individual" is obviously stretched by this asexual reproductive process.

Sex Should Be Losing

For biologists, the evolution of sex is a major puzzle. Sexual reproduction seems to have a built-in two-fold cost.

Why Sexual Reproduction Is a Puzzle

A parent goose with goslings swimming on a peaceful pond surrounded by greenery.

Why It Costs So Much

In many species, only half the population can physically bear young, and each parent passes on only 50% of their genes. Asexual reproduction avoids both of those losses.

Why Sexual Reproduction Is a Puzzle

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