April 18, 2009

• Megafauna and Gravity

  “Twelve thousand years ago, then.  When the Ice Age had retreated back to the North, and perhaps human beings settled in the mountains for the first time.  Wonderful creatures walked these hills then — the shaggy elephants called mastodons, American lions that would dwarf their modern African cousins, saber-toothed tigers, sloths bigger than pickup trucks, bears double the size of today’s grizzlies, birds of prey with wingspans of twenty-five feet, musk oxen, and camels, and horses.”

  Sharyn McCrumb, The Rosewood Casket, page 27

  Last night, I had switched to some fiction for lighter reading at bedtime, and encountered the passage above.  Thinking about those big animals of the past, and the even bigger megasaurians of a more distant past, I was reminded of several conversations Doug, Greyfox and I have had over monster movies.  Greyfox loves them, and willingly suspends his disbelief.  He knows about the square-cube law, and it doesn’t blunt his pleasure in impossibly big insects or killer tomatoes, at all.

  It occurred to me to wonder if, perhaps, one reason we don’t have anything that big these days is because gravity then was not as strong a force as gravity is now.  A lot of what-ifs ran through my head.  I recalled that heavier bodies have stronger gravitational fields.  It is assumed that several different factors, such as climate change and human predation, killed off a lot of big animals at the end of the Pleistocene Era.  However, fossils show that surviving descendants of some of those big species are not as big as the ancestors were.

  Then it occurred to me that geologists and paleontologists generally agree that the much earlier extinction of the dinosaurs, the K-T Extinction was precipitated by an asteroid impact off Yucatan.

  

  The fossil record shows that the impact event caused a disproportionately high number of extinctions in North America.  In an article in the November 1996 issue of Geology, planetary geoscientist Peter H. Schultz of Brown University in Providence, Rhode Island, and paleooceanographer Steven D’Hondt of the University of Rhode Island:

  …cite geological evidence that the asteroid or other object didn’t strike the Yucatan head-on; rather, it approached from the southeast and hit at an angle, perhaps 20 to 30 degrees from the horizontal.

  The impact forced the searing debris toward the northwest into a parabola-shaped kill zone over western and central North America. This “corridor of incineration,” as Schultz and D’Hondt called it, may have ranged beyond the Pacific shore and the Appalachian Mountains, and possibly all the way to Siberia.

  dinosauria.com

  One alternative theory for the cause of the mass extinctions at the end of the Cretaceous period is a lengthy series of volcanic eruptions close to the plate boundary between India and Africa, that were ongoing at the time of the impact and continued afterward.

  Enormous quantities of basalt flooded out over what is now the Deccan Plateau of western India to form huge lava beds called the Deccan Traps.

  The possible results of the Deccan Traps eruptions include acid rain, ozone depletion, a greenhouse effect, a cooling effect, or any combination of the above: in other words, many of the same effects cited for an asteroid impact.

  Richard Cowen, ucmp.berkeley.edu

  I see no reason to doubt that both events could have contributed to the mass extinctions of megafauna.  I can even think of a plausible scenario or two in which these events could have been interrelated.  What if Earth was passing through a debris field and had experienced many smaller meteorite impacts, some of which had struck that plate boundary and triggered exceptional volcanic activity?  Or, what if the gravitational effects of approaching space debris contributed to the upwelling of that gigantic magma plume and/or its emergence between the plates?

  But I digress.  My point was that it is not only possible but probable verging on inevitable that the earth has grown heavier, and continues to do so, due to the addition of material from space.  How significant would that be in terms of increased gravitational pull?  How critical would a slight increase be to a big animal?  I was looking for answers to these questions and more when I started my web search today.

  I was immediately pleased to find that someone had preceded me in speculating about the effects of attenuated gravity on megafauna… until I read the material I found.  Ted Holden‘s website apparently no longer exists, but I was able to bring it back with the help of the Wayback Machine.  He is a creationist whose ideas are broadly lampooned.  The man himself is called, variously, a bat, and a loon.  From what I’ve read, I’d say that’s insulting to small flying mammals and weird-sounding waterfowl.  There’s even a web quiz that will help you find out if you are Ted Holden.  I’m not.

  As far as creationism goes, I’m willing to accept that this finite observable universe and its evolving systems might have been set up by some being or force that transcends the finite and observable, but I don’t think it then stuck around to micromanage all the fiddly bits.  My theoretical god knows how to delegate authority.

  

  As a pleasant addition to a day of megafaunal research, quitchick dropped in with a link for me, about a man, Chris Gallucci, who loves elephants.  He works at Tippi Hedren’s Shambala Preserve in California.  I suppose there are many women who won’t see him as I do, but to me that is one helluva beautiful man.

  

  • 7:45 pm
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