Why ancient earth wasn't an iceball

One of the great science mysteries might finally have been solved - why wasn't ancient Earth covered in ice?

Back in the early days of our planet, it was mostly covered in seas. Since the Sun was warming much less back then, it has puzzled scientists why these seas were not frozen. Now Danish and US scientists offer an explanation.

Why Earth Wasn't One Big Ball of Ice 4 Billion Years Ago When Sun's Radiation Was Weaker

Scientists have solved one of the great mysteries of our geological past: Why Earth's surface was not one big lump of ice four billion years ago when Sun radiation was much weaker than today. Scientists have presumed that Earth's atmosphere back then consisted of 30 percent CO2 trapping heat like a greenhouse. However, new research shows that the reason for Earth not going into a deep freeze at the time was quite different.

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Now, however, Professor Minik Rosing, from the Natural History Museum of Denmark, and Christian Bjerrum, from the Department of Geography and Geology at University of Copenhagen, together with American colleagues from Stanford University in California have discovered the reason for "the missing ice age" back then, thereby solving the Sun paradox, which has haunted scientific circles for more than 40 years.

Professor Minik Rosing explains: "What prevented an ice age back then was not high CO2 concentration in the atmosphere, but the fact that the cloud layer was much thinner than it is today. In addition to this, Earth's surface was covered by water. This meant that the Sun's rays could warm the oceans unobstructed, which in turn could layer the heat, thereby preventing Earth's watery surface from freezing into ice. The reason for the lack of clouds back in Earth's childhood can be explained by the process by which clouds form. This process requires chemical substances that are produced by algae and plants, which did not exist at the time. These chemical processes would have been able to form a dense layer of clouds, which in turn would have reflected the Sun's rays, throwing them back into the cosmos and thereby preventing the warming of Earth's oceans.

So, the lack of life, which in turns leads to less clouds, and the liquid surfaces, are the reasons why the water didn't freeze, even when the heat from the Sun were lower.

This is a much better explanation than the earlier proposed explanation (also mentioned in the ScienceDaily article) that the CO₂ levels were much higher back then. The new investigation which led to the new explanation demonstrates that the CO₂ levels back then were higher, but nowhere nearly as much higher as the old explanation would have required.

The actual study is behind a paywall at Nature, but if you have access, you can find it here.

Ancient Greenlandic Genome Decoded

As one might expect, this has been fairly big news in Denmark, and it has now also been reported in the NY Times

Ancient Man in Greenland Has Genome Decoded

The genome of a man who lived on the western coast of Greenland some 4,000 years ago has been decoded, thanks to the surprisingly good preservation of DNA in a swatch of his hair so thick it was originally thought to be from a bear.

This is the first time the whole genome of an ancient human has been analyzed, and it joins the list of just eight whole genomes of living people that have been decoded so far. It also sheds new light on the settlement of North America by showing there was a hitherto unsuspected migration of people across the continent, from Siberia to Greenland, some 5,500 years ago.

The genome came from some hair which had been in a bag at the Danish National Museum since 1986. The hair were found in an ancient garbage heap.

The study was published in Nature and can be found here: Ancient human genome sequence of an extinct Palaeo-Eskimo

As the NY Times mentions, the research has now given new insight into the migration patterns of the ancient humans, demonstrating some unexpected paths.

This is probably something we'll continue to see when more and more ancient genomes are decoded, expanding our knowledge in this area.

Chimpanzees get AIDS too

This is really more the area of Tara or ERV but I still thought I'd comment on this piece of news.

African primates can be infected with over 40 different simian immunodeficiency viruses (SIVs). These diseases are related to two diseases which infects our particular species of primates, Homo sapiens, human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2) - indeed the two types of HIV are the result of SIVs crossing the species barrier.

HIV is considered an epidemic with more than 30 million people suffering from it worldwide (source - .pdf). As people hopefully know, HIV 1 and 2 will, if not treated by medicine, result in acquired immune deficiency syndrome (AIDS), which is fatal. 2 million people died from AIDS in 2007.

HIV and AIDS is one of the top prioritized areas of medical studies, and both the evolution of HIV from SIV and the connection between HIV and AIDS are well understood. This doesn't, however, keep some people from either claiming that HIV/AIDS is man-made, or that AIDS doesn't exist.

One of the arguments used by both groups is that SIV doesn't lead to AIDS in primates - the one group to argue that HIV couldn't have evolved from SIV, the other to argue that AIDS is not real.

Neither group makes sense. The lack of development of AIDS in SIV carrying primates is by no means evidence of there being no SIV-HIV connection, nor evidence of there being no HIV-AIDS connection.

Still, this matters even less now. Researchers have found out that some primates can get AIDS.

Nature has a new paper by Beatrice Hahn et al.

Increased mortality and AIDS-like immunopathology in wild chimpanzees infected with SIVcpz (link takes you to the abstract, the paper is behind a paywall)

African primates are naturally infected with over 40 different simian immunodeficiency viruses (SIVs), two of which have crossed the species barrier and generated human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2)1, 2. Unlike the human viruses, however, SIVs do not generally cause acquired immunodeficiency syndrome (AIDS) in their natural hosts3. Here we show that SIVcpz, the immediate precursor of HIV-1, is pathogenic in free-ranging chimpanzees. By following 94 members of two habituated chimpanzee communities in Gombe National Park, Tanzania, for over 9 years, we found a 10- to 16-fold higher age-corrected death hazard for SIVcpz-infected (n = 17) compared to uninfected (n = 77) chimpanzees. We also found that SIVcpz-infected females were less likely to give birth and had a higher infant mortality rate than uninfected females. Immunohistochemistry and in situ hybridization of post-mortem spleen and lymph node samples from three infected and two uninfected chimpanzees revealed significant CD4+ T-cell depletion in all infected individuals, with evidence of high viral replication and extensive follicular dendritic cell virus trapping in one of them. One female, who died within 3 years of acquiring SIVcpz, had histopathological findings consistent with end-stage AIDS. These results indicate that SIVcpz, like HIV-1, is associated with progressive CD4+ T-cell loss, lymphatic tissue destruction and premature death. These findings challenge the prevailing view that all natural SIV infections are non-pathogenic and suggest that SIVcpz has a substantial negative impact on the health, reproduction and lifespan of chimpanzees in the wild.

In other words, there is a non-trivial health cost in being infected with SIVcpz.

This is not a trivial finding. As Nature makes clear in it's news release on the story (Wild chimpanzees get AIDS-like illness) this will impact future research.

The results suggest that it will not be possible to find the key to HIV immunity in the chimpanzee genome, as scientists had hoped. However, the study, published in Nature, sets the stage for researchers to gain insight into how HIV and SIV cause disease in their hosts by studying the responses of different primates to the viruses. Wild monkeys that have coexisted with SIV for a long time — such as sooty mangabeys and African green monkeys — seem to have evolved the ability to control SIV, and so do not become ill when exposed to the virus. The new paper, however, shows that chimpanzees — which, like humans, were exposed to SIV more recently — are sickened by the virus.

NY Times also writes about this study: Chimpanzees Do Die From Simian AIDS, Study Finds

Update: Carl Zimmer has written a great blog post about this.

Lazy linking

I have a very firm deadline at the end of this month, so I am not much on the internet these days. Still, I've come across a few things that I thought I'd share.

Judge Returns Gray Wolves to Endangered List in NY Times

Allison Martell, a guest blogger over at Feminsite, writes about The puzzle of female entrepreneurs

The Electronics Junkyard Dismantlers of Guiyu

30 Creepiest Trees on Earth [pics]

Gallery: From Tiny Machines to Security, the Future of Nano-Fabrication

The 91st Skeptics’ Circle is up at Sorting Out Science

Epi Wonk’s Intro to Data Analysis

Old bomb found in whale

Updated - see below

Another data-point against whale hunting - these giants of the sea can become quite old.

19th century bomb found in whale

Scientists have retrieved a weapon fragment from a whale that suggests it may have swum its first strokes not long after the American Civil War.

The fragment is part of a time delay bomb that was introduced in 1879 and manufactured until 1885.

Scientists say it is rare to find a whale over 100 years old but believe some may reach 200.

The bowhead whale was killed by indigenous hunters off Alaska as part of their subsistence quota.

Experts think the wound was inflicted in about 1890.

That's about 120 years ago. So a whale that escaped death by whale hunting more than a century ago, was killed by whale hunting this year. Tragic.

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Edit: Triggerede by ERV's comment I did a little research into the living span of mammals, and it turns out that due to the discovery of the bomb and other discoveries, as well as chemical analysis of the levels of aspartic acid in the whales' eyes, Bowhead whales are now considered the oldest mammals. A honour previously thought to belong to Homo Sapiens.

And they are not the longest living by a small margin either.

Bada found that most of the adult whales were between 20 and 60 years old when they died, but five males were much older. One was 91, one was 135, one 159, one 172, and the oldest whale was 211 years old at the time of its death. That whale, alive during the term of President Clinton, was also gliding slowly and gracefully through the Bering, Chukchi and Beaufort seas when Thomas Jefferson was president.

Bada explained that the method of measuring changes in aspartic acid to determine age has an accuracy range of about 16 percent, which means the 211 year-old bowhead could have been from 177 to 245 years old.

The oldest known ages for mammals are 110 years for a blue whale and 114 years for a fin whale, based on a Japanese scientist's counting of waxy laminates on the inner ear plug of the whales, a method that does not work for bowheads. The oldest living person with a birth certificate was a 122-year-old woman from France who died in 1997. Elephants have lived to 70 in captivity, so bowheads may be the oldest mammals that exist.

Of course, non-mammals, such as parrots and turtles, are also know to live to great ages, so there are probably other animals that lives as long as the Bowhead whales.