Cambrian explosion

The Cambrian explosion, or less commonly Cambrian radiation, was the relatively short evolutionary event, beginning around 542 million years ago in the Cambrian Period, during which most major animal phyla appeared, as indicated by the fossil record. Lasting for about the next 20–25 million years, it resulted in the divergence of most modern metazoan phyla. Additionally, the event was accompanied by major diversification of other organisms. Prior to the Cambrian explosion, most organisms were simple, composed of individual cells occasionally organized into colonies. Over the following 70 to 80 million years, the rate of diversification accelerated by an order of magnitude and the diversity of life began to resemble that of today. Many of the present phyla appeared during this period, with the exception of Bryozoa, which made its earliest known appearance in the Lower Ordovician.

The Cambrian explosion has generated extensive scientific debate. The seemingly rapid appearance of fossils in the “Primordial Strata” was noted as early as the 1840s, and in 1859 Charles Darwin discussed it as one of the main objections that could be made against the theory of evolution by natural selection. The long-running puzzlement about the appearance of the Cambrian fauna, seemingly abruptly and from nowhere, centers on three key points: whether there really was a mass diversification of complex organisms over a relatively short period of time during the early Cambrian; what might have caused such rapid change; and what it would imply about the origin of animal life. Interpretation is difficult due to a limited supply of evidence, based mainly on an incomplete fossil record and chemical signatures remaining in Cambrian rocks.

PZ Myers

Paul Zachary "PZ" Myers (born March 9, 1957) is an American scientist and associate professor of biology at the University of Minnesota Morris (UMM). He is founder and author of the Pharyngula science blog, hosted on both the Science Blogs and Freethought Blogs networks. He currently works with zebrafish in the field of evolutionary developmental biology and cultivates an interest in cephalopods.

He is an outspoken critic of intelligent design (ID) and the creationist movement, and is active in the American creation–evolution controversy. He is widely regarded as a confrontationalist.

In 2006, the journal Nature listed his Pharyngula as the top-ranked blog by a scientist based on popularity.

Myers received the American Humanist Association's 2009 Humanist of the Year award and International Humanist Award in 2011. Asteroid 153298 Paulmyers is named in his honor.

Early life

Myers was born March 9, 1957, the eldest of six children in Kent, Washington; his mother is of Swedish and Norwegian descent. Regarding his ancestry, Myers wrote: "I'm only half Scandinavian. The blood has been thinned with that of those domesticated English and Irish and Scots." He was named "Paul Zachary", after his grandfather, but preferred the initials PZ to being called "Little Paul". He has described his family as "probably what would be called the working poor nowadays", and noted that "when I was growing up I was called white trash more than a few times".