Well, I entered, and my essay, "Improving Community Safety," won!
But the branch of the that readers might find most interesting led to humans. Humans are in the phylum, and the last common ancestor that founded the Chordata phylum is still a mystery and understandably a source of controversy. Was our ancestor a ? A ? Peter Ward made the case, as have others for a long time, that it was the sea squirt, also called a tunicate, which in its larval stage resembles a fish. The nerve cord in most bilaterally symmetric animals runs below the belly, not above it, and a sea squirt that never grew up may have been our direct ancestor. Adult tunicates are also highly adapted to extracting oxygen from water, even too much so, with only about 10% of today’s available oxygen extracted in tunicate respiration. It may mean that tunicates adapted to low oxygen conditions early on. Ward’s respiration hypothesis, which makes the case that adapting to low oxygen conditions was an evolutionary spur for animals, will repeatedly reappear in this essay, as will . Ward’s hypothesis may be proven wrong or will not have the key influence that he attributes to it, but it also has plenty going for it. The idea that fluctuating oxygen levels impacted animal evolution has been gaining support in recent years, particularly in light of recent reconstructions of oxygen levels in the eon of complex life, called and , which have yielded broadly similar results, but their variances mean that much more work needs to be performed before on the can be done, if it ever can be. Ward’s basic hypotheses is that when oxygen levels are high, ecosystems are diverse and life is an easy proposition; when oxygen levels are low, animals adapted to high oxygen levels go extinct and the survivors are adapted to low oxygen with body plan changes, and their adaptations helped them dominate after the extinctions. The has a pretty wide range of potential error, particularly in the early years, and it also tracked atmospheric carbon dioxide levels. The challenges to the validity of a model based on data with such a wide range of error are understandable. But some broad trends are unmistakable, as it is with other models, some of which are generally declining carbon dioxide levels, some huge oxygen spikes, and the generally relationship between oxygen and carbon dioxide levels, which a geochemist would expect. The high carbon dioxide level during the Cambrian, of at least 4,000 PPM (the "RCO2" in the below graphic is a ratio of the calculated CO2 levels to today's levels), is what scientists think made the times so hot. (Permission: Peter Ward, June 2014)
Ive flown before, but never without my parents.
Alvarez, was really friendly and easy to talk to.
Today, people practicing the hunter-gatherer lifestyle are usually dependent on the production of nearby agricultural societies. Pure hunter-gathering, of the kind performed before the Domestication Revolution, has almost entirely vanished.
She also introduced me to the other contest winners.
Darwin , but believed that natural selection primarily worked at the individual level. The idea of group selection has , if . Anthropologists and biologists see evidence of group selection, not only in social creatures such as , but also in the ability of human societies to survive competition with their neighbors. Hunter-gatherer societies eliminated disruptive members by , which has been argued to have been reflected genetically in eliminating uncooperative people from society. Those kinds of activities may have helped cull the human herd of “uncooperative” genes. When Europe conquered the world, it had the highest energy usage, by far, of any peoples on Earth, which was why it always prevailed. When high-energy societies met low-energy societies, the results were almost always catastrophic for low-energy societies. Hunter-gatherer societies have no chance in a competition with societies possessing domesticated plants and animals, much less industrialized societies. Whether they are species or human civilizations, the determines their viability.