Climate Change
gregladen | April 18, 2008Good question ... what IS in the air?
The simple answer is that the air ... the Earth's atmosphere ... is about 78% nitrogen, 21% oxygen, with a tiny amount of some other gases including water vapor. Then, there's dirt. I want to talk a little about the oxygen, one of the other gases (carbon dioxide to be exact), the water vapor, and the dirt.
Oxygen
The oxygen is one of the most important parts to us because we (and all the other animals) need it to breath. To me, what is most interesting about the oxygen is that in the old days ... before any animals or plants evolved but life…
gregladen | April 7, 2008Ever since 3,599 years ago humans have been asking the question "Why did our furry elephant go extinct?"
What caused the woolly mammoth's (not to be confused with the also-woolly mastodon) extinction? Climate warming in the Holocene might have driven the extinction of this cold-adapted species, yet the species had survived previous warming periods, suggesting that the more-plausible cause was human expansion.
The woolly mammoth went extinct less than four thousand years ago. The bones of miniaturized woolly mammoths have been found in Siberia dating to about 3,600 years ago. Indeed,…
gregladen | April 6, 2008
Grrrrrrrrrrrrr....
Welcome to the Lucky 13th Edition of The Boneyard ... the Web Carnival about Bones and Stuff.
"The Boneyard is a blog carnival covering all things paleo, from dinosaurs to pollen to hominids and everywhere in between. It's held every two weeks (the 1st and 3rd Saturday of the month), traveling around to a different blog for each installment, connecting some of the best blogging on ancient life."
The previous edition of The Boneyard is here, at Dragon's Tales. The next edition of The Boneyard will be Here at Archaeozoology. If you would like to submit an entry to the next…
gregladen | March 27, 2008Old books can be wonderful sources of information, ideas, and even inspiration. I collect them and sometimes even read them. Reading a 100 year old book in your field of interest is a challenge and can be a rewarding experience.
It is a challenge because it is dangerous. I worry that I might accidentally learn something that is no longer true. What if I remember it at some later time, like at a cocktail party or while giving a lecture, but don't remember the source: "... As is well known, flies spontaneously generate from certain forms of mud ..."
Repost from gregladen.com ... apropos…
gregladen | March 26, 2008Welcome to Berry Go Round #3, the blog carnival deicated to all things botanical.
The previous installment, Berry Go Round #2, is located here, at Further Thoughts. If you would like to submit an item to the next Berry Go Round, you may use this handy submission form. The Berry Go Round Home Page is here.
Let us begin right away with the Artichokes. Seeds Aside has a piece on the relationship between the artichoke and the cardoon, both known in ADL (ancient dead language) as Cynara cardunculus. The phyloge relatinship between the two, and the story of domestication for each, is very…
gregladen | March 19, 2008During Earth Hour, you switch off the lights and other non-essential electronic devices. At 8:00 PM March 29th. You'll save electricity, but more importantly, you'll be making a point.
Created to take a stand against the greatest threat our planet has ever faced, Earth Hour uses the simple action of turning off the lights for one hour to deliver a powerful message about the need for action on global warming.
This simple act has captured the hearts and minds of people all over the world. As a result, at 8pm March 29, 2008 millions of people in some of the world's major capital cities,…
gregladen | March 12, 2008
The pending federal decision about whether to protect the polar bear as a threatened species is as much about climate science as it is about climate change.
The US Fish and Wildlife service is contemplating the listing of the obviusly endangered polar bear as a threatened species. Well, duh...
The problem for them (the US Federal Government, which has been converted over the last 7 years into a right wing think tank) is that the main threat to the polar bear is global warming, and there are still plenty of individuals in charge of the US that want to deny global warming.
But, with…
gregladen | March 7, 2008Scientists have long projected that areas north and south of the tropics will grow drier in a warming world -- from the Middle East through the European Riviera to the American Southwest, from sub-Saharan Africa to parts of Australia.
These regions are too far from the equator to benefit from the moist columns of heated air that result in steamy afternoon downpours. And the additional precipitation foreseen as more water evaporates from the seas is mostly expected to fall at higher latitudes. Essentially, a lot of climate scientists say, these regions may start to feel more like deserts under…
gregladen | March 6, 2008There is a fairly new paper in PLoS on the colonization of the New World. It is the latest in a series of attempts to synthesize biogeography, climate change related paleoenvironmental reconstruction, genetics, and archaeology.
The authors draw these conclusions:
These results support a model for the peopling of the New World in which Amerind ancestors diverged from the Asian gene pool prior to 40,000 years ago and experienced a gradual population expansion as they moved into Beringia. After a long period of little change in population size in greater Beringia, Amerinds rapidly expanded into…
gregladen | February 22, 2008In 1833, Darwin spent a fair amount of time on the East Coast of South America, including in the Pampas, where he had access to abundant fossil material. Here I'd like to examine his writings about some of the megafauna, including Toxodon, Mastodon, and horses, and his further considerations of biogeography and evolution.
In the vicinity of Rio Tercero...
Hearing ... of the remains of one of the old giants, which a man told me he had seen on the banks of the Parana, I procured a canoe, and proceeded to the place. Two groups of immense bones projected in bold relief from the perpendicular…
gregladen | February 19, 2008
Fallback foods are the foods that an organism eats when it can't find the good stuff. It has been suggested that adaptive changes in fallback food strategies can leave a more distinct mark on the morphology of an organism, including in the fossil record, than changes in preferred food strategies. This assertion is based on work done by the Grants and others with Galapagos Island finches, by Richard Wrangham and me with hominids, and by Betsy Burr and me with rodents.
The reason for this is simple. There is a rough correspondence between how much energy one can obtain from a food type and…
gregladen | February 18, 2008Charles Darwin wrote a book called Geological Observations on South America. Since Fitzroy needed to carry out intensive and extensive coastal mapping in South America, and Darwin was, at heart, a geologist more than anything else (at least during the Beagle's voyage), this meant that Darwin would become the world's expert on South American geology. Much of The Voyage is about his expeditions and observations. Part of this, of course, was figuring out the paleontology of the region.
Bahia Blanca is a port at the northern end of Patagonia. Chapter V of The Voyage begins:
THE Beagle…
gregladen | February 3, 2008Behold this humble passage by Darwin, which is what immediately follows his discussion of the octopus. This passage is a touchstone to several important aspects of what Darwin was doing and thinking, and is a poignant link to what Darwin did not know:
ST. PAUL'S ROCKS.--In crossing the Atlantic we hove to, during the morning of February 16th, close to the island of St. Paul.
Ah, sorry to interrupt. Saint Paul's Rocks are in the Atlantic roughly half way between South America and Africa. That geographical information should give you a hint of why these rocks are important!
"Hove to"…
gregladen | January 31, 2008
Proposals to give the latter part of the present geological period (the Holocene) a new name ... the Anthropocene ... are misguided, scientifically invalid, and obnoxious. However, there is a use for a term that is closely related to "Anthropocene" and I propose that we adopt that term instead.
The pithy title of the paper making this proposal is "Are we now living in the Anthropocene" (sic: no question mark is included in this title, enigmatically).
It is not an entirely stupid idea. The paper argues that there are major changes of the type often used to distinguish between major…
gregladen | January 27, 2008The loss of sight in cave dwelling species is widely known. We presume that since sight in utter darkness has no fitness value, the mutation of a gene critical to the development of the sense of sight is not selected against. Over time, any population living in darkness will eventually experience experience such mutations, and these mutations can reach fixation.
Astyanax mexicanus: Top is the surface, sighted form, bottom is the cave-dwelling, blind form. From the Jeffery Lab.Beyond this, we may hypothesize that a mutation "turning off" sight could be beneficial. By definition, an…
gregladen | January 25, 2008
Did humans wipe out the Pleistocene megafauna? This is a question that can be asked separately for each area of the world colonized by Homo sapiens. It is also a question that engenders sometimes heated debate. A new paper coming out in the Journal of Human Evolution concludes that many Pleistocene megafauna managed to go extinct by themselves, but that humans were not entirely uninvolved.
The paper by Pushkina and Raia ("Human influence on distribution and extinctions of the late Pleistocene Eurasian megafauna") examines sources in the literature and a number of databases for Eurasian…
gregladen | January 24, 2008The amount of ice lost to the sea from Antarctica has increased by 75 percent in the last 10 years. This is the result of an increase in glacial flow. It had previously been thought, and perhas was the case, that Greenland ice loss outpaced the Antarctica. This is no longer the case.
An article coming out in the next issue of Nature Geoscience, by Rignot et al ("Recent Antarctic ice mass loss from radar interferometry and regional climate modelling") is the most detailed study of this phenomenon to date.
There are two factors that affect the flow of ice into the sea at the edge of the…
gregladen | January 23, 2008The end-Permian mass extinction event was the big daddy of all the known mass extinction events. Life on the planet Earth was almost entirely wiped out. A new paper explores the post-extinction recovery of ecological systems.
Post extinction dynamics can be understood in relation to several dimensions: Taxonomy (the range and structure of different taxonomic groups); ecology (the interrelationship between the new species and the niches available, as well as the structure and distribution of those niches); and morphology (the overall morphospace filled by the new taxa). The present study…
gregladen | January 18, 2008"A University of Alberta Arctic ice researcher is closing in on some real understanding about the process that might be feeding rising sea levels."
Using satellite microwave data, Martin Sharp, a professor in the Department of Earth and Atmospheric Sciences, has helped lead a team of researchers who remapped the summer melt extent and duration across Greenland for a five-year period stretching from 2000 to 2004.
"What we're interested in is the problem of explaining why the rates of global sea level rising have more or less doubled since the early 1990s compared with the early part of the…
gregladen | January 17, 2008Things are just not like what they used to be. You know this. You know that the Age of Dinosaurs, for instance, was full of dinosaurs and stuff, and before transitional fossil forms crawled out of the sea to colonize the land, all animals were aquatic, etc. But did you know that from a purely modern perspective, the Miocene was the most important geological period?
First, lets get one thing straight. We are not in the so-called "Holocene." The so-called "Holocene" is a totally bogus geological period. Saying "Hey, we're in the Holocene, not the Pleistocene ... the Pleistocene is over…