Combining fossil dates and the DNA analysis, Peterson, Erwin and their colleagues conclude that the basic genetic tools for fancy animal bodies arose long before a surge of evolutionary innovation around the Cambrian period
gave rise to modern animal groups.
The Cambrian Period
, marked by a rapid diversification of life-forms on Earth as well as the rise of mineralized organisms, ranges 542-488 million years ago.
The race started after researchers uncovered jellyfish embryos in 540-million-year-old rocks from the early Cambrian period
, a time of explosive animal evolution (SN: 11/15/97, p.
The predator, tracked by researchers from the University of Saskatchewan and Royal Ontario Museum (ROM) ruled the seas of the Cambrian period
The organism, which lived more than half a billion years ago, flourished alongside a broad array of unclassifiable species that filled the oceans immediately before the explosion of animal life in the Cambrian period
The new study has revealed details as to how oxygen came to vanish from Earth's ancient atmosphere during the Cambrian Period
, only to return at higher levels than ever before.
The new work builds on research by Chinese scientists, who 20 years ago described egglike fossils in rocks from the early Cambrian period
This could also explain how some microorganisms survived the period and went on to flourish and diversify during the later Cambrian period
Before the Cambrian period
, almost all life was microscopic, except for some enigmatic soft-bodied organisms.
And not until the Cambrian period
, which began about 542 million years ago, were large, complex organisms commonplace.
A team of paleontologists working in Mongolia has discovered the earliest conclusive evidence that sponges thrived on the seafloor just before the start of the Cambrian period
544 million years ago.
Smith said: "It's long been thought that cephalopods evolved in the Late Cambrian period
, when gradual modifications to the shells of creeping, snail-like animals made them able to float.
Charles Darwin and generations of biologists since him have struggled to explain the sudden appearance of animal fossils just after the start of Earth's Cambrian period
, 543 million years ago.
The Cambrian period
, known for the "Cambrian Explosion" that saw the sudden appearance of all the major animal groups and the establishment of complex ecosystems, was followed by the "Great Ordovician Biodiversification Event," when the number of marine animal genera increased exponentially over a period of 25 million years.
The Ordivician: Life's second big bang - The Cambrian period
, starting about 540 million years ago, is famous for the appearance of all but one of the types of creatures we see around us today.