Cambrian Explosion Explanations

Duck and cover! It’s the Cambrian Explosion!

Here’s a brief over view of evolution: Life started 3.5+ billion years ago. Then nearly nothing happens during the ‘boring billion’, as it’s affectionately known (with a lot of neat exceptions, like the Ediacaran fossils etc.). Then 580+- million years ago there was an ‘explosion’ of phylum constituting most of the 36 animal phyla now in existence. Some paleontologist estimate that as many as a 100 phylum were created over the period of only tens of millions of years. What gives? Why the billion years of nothing and then an explosion of diversity? Why haven’t we had a continuation or acceleration of this diversification? How come we’ve only added a hand full more phyla? Why hasn’t the pace continued? This blog will dabble in some of the exciting developments that have emerged in this exciting inquiry.

• Hox Genes: Evolution only works by mutations.  ONLY.  That means it can take a stupefyingly long time for big changes since big mutations are rare and the amount of big changes that are positive is vanishingly small.  So, when a break through mutation happens, like in the hox genes (those genes that regulate embryonic development of body shape) that can give a whole new range of possibilities for evolution to play with.  That is most likely what happened during the Cambrian Explosion - major developmental genes were developed and the landscape was drastically changed.

• Snowball Earth: If you don’t know about this, you are positively missing out.  Several times in the Earth’s history our planet has looked like the ice cube Europa.  Support for this includes evidence of glacier deposits at the then equator (based on paleomagnetism, marine sedimentation), and other chemical markers (like pH indicators, oxygen markers in iron deposits, iridium meteorite deposits, carbon isotope ratios, carbonite deposits, etc.)  The last major Snowball Earth period was right before the so called Cambrian Explosion.  This thaw out might have been the crack in the dam that had been building for some time.

Europa, one of the moons of Jupiter.

Artist's rendition of what Earth may have look like as a snowball.

• Oxygen Levels: This chemical is a major limiting factor for life.  One might argue that we are oxygen powered animals since it serves such a vital function in making our energy.  There’s more to it than just energy, though.  What’s the most common protein in our body accounting for some 25-35%? Collagen.  What’s collagen need a whole lot of to be made?  Oxygen!  What’s it do?  It sticks cells together to make multicellular life and larger structures possible! So, during the Snowball Earth a massive amount of rock was pulverized and dropped into the ocean essentially as fertilizer to cyanobacteria that went nuts growing after the ice sheets melted away thereby producing a prodigious spike in oxygen levels.

That first bump up is the Cambrian Explosion.

• Predation: Things had been eating each other for a long time, but not really at a multicellular level.  During the Cambrian Explosion an arms race took place to hunt and escape that resulted in some amazing adaptations.
• Eyes: predation went from passive filter feeding to active hunting.

• Hard and Bony Parts: Being able to chew and have armor changed everything.

• Mouth: Just think sponge and jellyfish if you want kind of want to know what life was like before the C.E.  Jaws changed everything.

Gotta love the names of Cambrian stuff.  This is anomalocaris (from anomaly).   

So, why so little phylum generation since then?...Let me know if you have other thoughts, but I'd imagine that much of it would have to do with so many of the environmental niches being filled already...But, I'm open to other ideas!

Pix from here, here, here, here, here, here, here, here, here, here, here, here, here, here, and here.

Cooperation Outcompetes Competition - The Evolution of Morality

When people don't believe in evolution it's never because of science. It's for religious reasons often masquerading as moral reasons:

Darwinian ‘survival of the fittest’ ideas thus powerfully shaped Stalin’s approach to society. Oppression, self glorification, atheism and murder resulted from Stalin’s rejection of his Creator after reading and believing the evolutionary ideas of Darwin. And the most tragic aspect of all? That while Stalin was turning his back on his Creator, he was building his philosophy on a lie. http://www.answersingenesis.org/creation/v10/i4/stalin.asp

Hitler’s understanding of the history of life, and that of Marx, Stalin and Mao, was not devised by a German, Russian or Chinese. It was shaped by an Englishman named Charles Darwin. http://www.answersingenesis.org/creation/v27/i2/darwin.asp

Those quotes are, of course, complete rubbish, but, in some ways, understandable. Humans have an innate fear of nature. Predators, poisonous snakes, spiders and harsh elements eliminated those of our ancestors that weren't afraid of nature on some level. I think it's possible that this evolved fear might be a partial explanation of why people fear evolution - a purely natural explanation of our own origins.

This negative, almost condemning tone, can even be seen in Darwin's choice of words, or more accurately, the public's choices of Darwin's words (since he wrote much on altruism as well) . The full title, often unknown, of Darwin's most well known book is: On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. The most quoted section of this watershed book ends speaking of the "war of nature, from famine and death.” One can attribute this bellicose view of nature from his contemporary Europe that was in the throws in industrialization, colonization, political turmoil, Marxism, and Malthusian philosophy, poets like Tennyson who spoke of nature being "red in tooth and claw" and even Freud, who in Civilization and Its Discontents spoke of renunciating 'animal' passions.

There's so much more to the story, though! Thankfully, many great scientists/writers are bringing this message to the public (EO Wilson, Kropotkin, Matt Ridley, Frans deWaal, Robert Wright, et al).

Here's why this matters: identity proceeds activity.

Creationists (nor evolutionists) need to be afraid of learning about our past, though. Nature is nice. Evolution is a pragmatist to the extreme and the bottom line is that cooperation works. It's not just polite, it's a smart long term strategy.

Controversial thesis: nearly every major revolution in evolution is the result of cooperation. Let's take a look.

• The First Life - 4 Billion years ago- The first life, our cenancestor, was a community of gene, metabolism, protein sharing organisms. Living came from nonliving as a team.

• Gaia - 3.5-2.0 bya -- Cyanobacteria produce enough oxygen as a by product of photosynthesis that the Earth's atmosphere is drastically change enough that the Earth 'rusted' causing iron in the ocean to dissipate and produce most of today's iron deposits. This 'pollution' also paves the way for future complex aerobic life to evolve.
• What Earth's atmosphere would look like without life:
• 98% Carbon dioxide
• 0% Oxygen
• 1% Nitrogen
• What Earth's atmosphere actually looks like, since life has drastically changed it:
• .00035 % Carbon dioxide
• 21% Oxygen - not too little to be anemic and not too much to have rampant oxidation, mutation and out of control conflagrations
• 78% Nitrogen - highly stable, wonderfully innocuous media
• Source: James Lovelock's Gaia

• Endosymbiosis - 2.0 bya - Scientists like Lynn Margulis looked at mitchondria, the powerhouse of our cells and other eukaryotes, and said, "Gee-whiz, these mitchondria divide like bacteria, have protein making ribosomes like bacteria, have their own unnucleated genome like a bacteria, are structurally shaped like a bacteria...I wonder if they once were bacteria!!??!" When you think about it, it's a shocking proposition. We, and other eukaryotes aren't one thing, we're many things working together. We aren't a human. We're trillions of evolved bacteria working together, bacteria that if you were to separate us from our friends, the mitchondria, we'd quickly die, as would they. This genius idea might have come about as aerobic bacteria (the mitchondria) and anaerobic bacteria (that'd be 'us', so to speak) dividing the labor, became specialists and after billions of years are absolutely, completely, 100% dependent on each other. Marvelous!

 

• 1 bya -- Multicellular life further refines the idea of working as a team of specialists. As oxygen continues to build up in the atmosphere, complex organic molecules like collagen, that use oxygen, can start to stick stuff together to build the vast city scape networks of multicellular life.

“...Astonishing is the thought that a human body consists of 10 trillion cells and that a brain contains about 100 billion neurons and 100 trillion synapses.” --William R Murry in the essay Grandeur in This View

• Sex - 600 mya -- Organisms wise up and start sharing the best of their DNA in exchange for the best of another organism's DNA thus 'spawning' a revolutionary new way of evolving - sexual recombination, the shuffling of genes. Another major advantage is having a bank of reserve genes stored in recessive genes.

 

“DNA in a single cell of our bodies, so small we cannot see it, if stretched out would reach from fingertip to fingertip of our outstretched arms and that there are trillions of cells in a body and that there is enough DNA in those cells to reach to the sun and back, can fill us with profound amazement." --William R Murry in the essay “Grandeur in This View”

• Digestion - 600 mya?-- Simple animals with the first digestive tracts co-evolve with bacteria (and later fungi and protists) to digest food more completely. Consider ourselves. By count, we are more bacteria than human. It's been estimated that a normal person has 10 trillions cell, but on and in us we have100 trillion bacteria cells. Once again, on another level, we are cooperation on legs.

• 500 mya -- Plants colonize the land possibly by the symbiosis of fungi (structure) and cyanobacteria (food production).

  

• 200mya - Mammals - What makes us so different from other organisms? How is that we rule the Cenozoic? Warm blood? No, think of other warm blooded animals like birds and arguably dinosaurs. Is it having fur? Not really. Feathers are probably more effective at retaining heat. Is it our differentiated teeth. Eh. I think what makes us special is the way we take extraordinarily good care of our young - we feed them milk through mammary glands. The child offers a way to pass on the mother's DNA and the mother offers milk. Cooperation, care, maternal love.

• 140 mya-- Which came first? Dinosaurs or flowering plants? It blows my mind that the correct answer is dinosaurs. For hundreds of millions of years there were forests without any flowers or vivid color, just seas of mostly green. Flowering plants evolved using insects as pollinators and animals as seed distributors. They now out number ferns and conifers 20 to 1. Cooperation works. There are 300,000 species of plants and the newcomers, flowering plants, number 250,000. If there were no flowering plants there'd be none of our normal fruit, butterflies, honey bees, cotton, roses, orchids, or us since our ancestors were fruit eaters, frugivores.

These are native to Florida - passion flower!

• 6 mya - 2 mya -- Alloparenting, gives Homo sapiens the ability to provide food for large brained, feeble offspring. "It takes a village to raise a child" really is true for humans. As our brains got bigger, our bodies got smaller (since there were selective forces that were keeper our hips small, like needing to run fast) and our babies started to need so much care that one woman couldn't do it alone, nor could one couple. A whole village was needed - someone to get carbs, like digging up tubers, several men to hunt meat collectively, another to gather fruits and nuts, another to bring water home, etc, etc. Contrast this with wildebeests that have to stand within minutes and join the herds migration or become dinner. Our babies can even raise their head, roll over or walk for a considerable time - often a year before walking!

• You can of course continue this line of thinking including cultural adaptations of cooperation like spoken language, agriculture, government, written language, et cetera.
• Human cooperation written in the fossil record.

Yes, there will always be parasites and heterotrophs using short term strategies that take advantage of other organisms, but there must, necessarily, obligatorily be more cooperation than all out competition otherwise the ecosystem will collapse.

Long term, cooperation out competes competition.

Nature is nice.

Images from here, here, here, here, here, here, here, here, here.