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WonderEvolutionary history fact

In the Cambrian explosion, which began about 538 million years ago, most of the major animal groups alive today appeared in the seas within roughly 20 million years, among them the first arthropods, molluscs and early relatives of vertebrates.

Cambrian explosion

EvolutionBiologyScienceOcean

The story behind the card

The name makes it sound sudden, but the Cambrian explosion unfolded over millions of years and built on the simpler life of the preceding Ediacaran period. What changed was the sheer variety: eyes, legs, shells and hard skeletons appear, along with burrows and the first clear signs of predators hunting prey. Two exceptional fossil beds preserve even soft tissue: Chengjiang in China, about 518 million years old, and the Burgess Shale in Canada, about 508 million years old. Trilobites, armoured sea-floor arthropods, appear early in the period and survived for some 270 million years. Leading explanations for the burst include rising oxygen in the oceans, new genetic tools for building bodies, and an arms race between predators and prey.

Türkçe oku
Yaklaşık 538 milyon yıl önce başlayan Kambriyen patlamasında, bugün yaşayan başlıca hayvan gruplarının çoğu 20 milyon yıl kadar içinde denizlerde ortaya çıktı. İlk eklembacaklılar, yumuşakçalar ve omurgalıların erken akrabaları da bunlar arasındaydı.

Adı ani bir olayı çağrıştırsa da Kambriyen patlaması milyonlarca yıla yayıldı ve kendinden önceki Ediacara Dönemi'nin daha basit canlıları üzerine kuruldu. Asıl değişen çeşitlilikti. Gözler, bacaklar, kabuklar ve sert iskeletler bu dönemde ortaya çıkar; deniz tabanına kazılmış oyuklar ve avcıların av peşine düştüğünü gösteren ilk açık izler de öyle. İki olağanüstü fosil yatağı yumuşak dokuları bile korumuştur: Çin'deki yaklaşık 518 milyon yıllık Chengjiang ve Kanada'daki yaklaşık 508 milyon yıllık Burgess Şeyli. Deniz tabanında yaşayan zırhlı eklembacaklılar olan trilobitler dönemin başlarında ortaya çıktı ve 270 milyon yıl kadar varlığını sürdürdü. Bu ani çeşitlenme için öne sürülen başlıca açıklamalar, okyanuslarda artan oksijen, beden kurmaya yarayan yeni genetik araçlar ve avcılarla avları arasındaki silahlanma yarışıdır.

Sources and further reading

Background reading: Cambrian explosion
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