Goodbye, eggshell: How pregnancy emerged in the animal world

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Goodbye, eggshell: How pregnancy emerged in the animal world

the gist

Live birth has evolved from egg-laying more than 100 separate times in lizards and snakes, far more often than in any other animals, while mammals did it only once. The first step is simply holding the egg inside the body for longer, which mostly happens in cold climates where a mother's warmth helps embryos develop. As the egg stays in, its shell thins until it disappears, and the mother starts passing water and nutrients across, the start of a placenta. Over time the embryo relies less on its yolk and more on its mother.

how it works

Eggs retained inside the mother keep warm in cold places. Selection then favours thinner shells, since these allow more gas and water exchange with the mother, and finally nutrient transfer.

so what

Live birth is a major evolutionary shift, and reptiles show it as a gradual series of small steps in many lineages, helping explain how pregnancy evolved in other animals, including humans.

fun fact

Some species, like the Australian skink Saiphos equalis, lay eggs in some populations and give birth in others.

D. W. Griffith’s A Corner in Wheat (1909)

the gist

In 1909 D. W. Griffith made a 14-minute film about a speculator who corners the wheat market and doubles the price of bread. A farmer sows his field while a 'Wheat King' gambles in the Chicago wheat pit; bakers raise the loaf from five cents to ten and the poor line up for bread. Griffith cut back and forth between the farm, the feast and the breadline, a technique called parallel editing, so audiences saw both ends of the economy at once. The film drew on Frank Norris's stories and on a real scheme: months earlier Chicago financier James Patten had cornered wheat, sent bread prices up and made about $5 million, roughly $185 million today.

how it works

To corner a market, a trader buys up most of the available supply and the futures contracts that promise more. Anyone who has to deliver the commodity must then buy from the cornerer at whatever price is demanded. The trader profits until the stock is released or the scheme collapses.

so what

A century on, it still shows how markets can be rigged by someone who controls supply, and how the people at either end, farmers and eaters, pay for it. It also helped establish editing as a way to argue a point, not just tell a story.

the bigger pattern

Corners have recurred whenever supply could be locked up, from the Hunt brothers' attempt on silver in 1979 to 1980 to the 'Black Friday' gold panic of 1869. Many such schemes end by collapsing, and the response is often new rules on speculation.

fun fact

In the film the Wheat King dies by falling into a grain elevator and being buried in the wheat he hoarded, an ending borrowed from Norris's novel The Octopus.

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