Saturday, September 27, 2014

Human teeth at dig put modern humans in China 70,000 to 126,000 years ago

Humans are a traveling species, and maybe they always have been.

New evidence suggests that humans—or something very close to humans—traveled out of Africa and into Asia far, far earlier than most modern models suggests. 

(Images: Two teeth that appear likely to be from anatomically modern humans; paleoanthropologist Christopher Bae at a fossil dig. Credit: University of Hawai`i at Mānoa.)

University of Hawai`i paleoanthropologist Christopher Bae, is the lead author on a paper that reports on human remains from China that date back roughly 125,000 years.

(Citation: Christopher J. Bae, Wei Wang, Jianxin Zhao, Shengming Huang, Feng Tian and Guanjun Shen, Modern human teeth from Late Pleistocene Luna Cave [Guangxi, China], DOI: 10.1016/j.quaint.2014.06.051)

Current theory has modern humans leaving Africa 60,000 years ago, but Bae and his co-authors found human teeth dating to between 70 and 126,000 years ago. They found the material in the Lunadong cave in China’s Guangxi Zhuang Autonomous Region, north of Vietnam.

It suggests there was not just one Out of Africa migration, but at least two, and possibly several.

“The findings from the Lunadong study clearly indicate that certain aspects of the Out of Africa model need to be rethought. That is, that there was at least one other earlier Out of Africa migration event that predated 60,000 years ago. 

“This paleoanthropological find, in addition to other recent studies from western and southern Asia, suggest that modern humans may have dispersed out of Africa in multiple waves rather than as one major single migration event 60,000 years ago as commonly thought,” said Bae, in aUniversity of Hawai`i press release.

There were numerous other human-like creatures traveling the world from their African homeland far earlier than this. Neandertals, Homo erectus and others were clearly moving across the landscape. Peking Man, whose remains were found in the 1920s near Beijing, dates to more than half a million years ago. He is considered a variety of Homo erectus.

© Jan TenBruggencate 2014

Sunday, September 21, 2014

Scary stuff: Great Barrier reef growth down 40%, world (and U.S.) carbon production stll increasing

The ravages of climate change thunder onward, and recent science doesn’t provide much hope.

Coral decline has been an issue, associated with coral disease, coral bleaching and lots more. A new study indicates the problems just keep coming. And our use of carbon is (surprise!) still climbing.

(Parenthetically, it’s election season. You need to ask every candidate whether they deny climate change, in which case don't vote for them, And more importantly, ask what they’ll do to combat it. And vote accordingly.)

A 30-year study of Australia’s Great Barrier Reef shows that coral growth has dropped an astounding 40 percent. Here is the ScienceDaily story on that. 

The abstract of the paper, published in the journal Geochimic et Cosmochimica Acta, suggests pretty clearly that ocean acidification—a result of increased carbon dioxide in the atmosphere—is the cause: 

“The similarity between the predicted and the measured decrease in (calcification) suggests that ocean acidification may be the primary cause for the lower CaCO3 precipitation rate on the Lizard Island reef flat.”

We're not aware of similar studies in the Hawaiian Islands, but it's reasonable to conclude that if it's happening on the largest reef system in the world, it might be happening elsewhere.

And, for all the talk, we’re not having much of an impact on the problem. Carbon dioxide emissions by human activities, far from declining or even staying level, are increasing. 

They're increasing more than the global average in the United States, India and China. The European Union has decreased carbon release, although it continues to import large amounts of goods from China, so it effectively shifts some of its carbon production there.

This is, of course, maddening. It’s like being on a careening bus, headed for a cliff, and being unable to agree to use the brakes.

A new study by the United Kingdom’s Tyndall Centre for Climate Change Research and the College of Engineering, Mathematics and Physical Sciences at the University of Exeter, says carbon dioxide releases into the atmosphere will rise in 2014 by another 2.5 percent, to 40 billion tonnes.

As the Great Barrier Reef inquiry and myriad other studies show, the results are bad already. But they can and will get worse. Many scientists feel that 2 degrees Celsius is a tipping point for catastrophic change.

"We have already used two-thirds of the total amount of carbon we can burn, in order to keep warming below the crucial 2°C level. If we carry on at the current rate we will reach our limit in as little as 30 years' time–and that is without any continued growth in emission levels. 

"The implication of no immediate action is worryingly clear—either we take a collective responsibility to make a difference, and soon, or it will be too late," said Pierre Friedlingstein, a professor at Exeter and lead author of the paper. 

Need some data points? This is from a press release from the University of East Anglia:

    China's CO2 emissions grew by 4.2 per cent in 2013, the USA's grew by 2.9 per cent, and India's emissions grew by 5.1 per cent.
    The EU has decreased its emissions by 1.8 per cent, though it continues to export a third of its emissions to China and other producers through imported goods and services.
    China's CO2 emissions per person overtook emissions in the EU for the first time in 2013. China's emissions are now larger than the US and EU combined. 16 per cent of China's emissions are for goods and services which are exported elsewhere.
    Emissions in the UK decreased by 2.6 per cent in 2013 caused by a decline in the use of coal and gas. However the UK exports a third of its emissions by consuming goods and services which are produced elsewhere.
    CO2 emissions are caused primarily by burning fossil fuels, as well as by cement production and deforestation. Deforestation accounts for 8 per cent of CO2 emissions.
    Historical and future CO2 emissions must remain below a total 3,200 billion tonnes to be in with a 66 per cent chance of keeping climate change below 2°C. But two thirds (2,000 billion tonnes) of this quota have already been used.
    If global emissions continue at their current rate, the remaining 1,200 billion tonnes will be used up in around 30 years – one generation.
    Global emissions must reduce by more than 5 per cent each year over several decades to keep climate change below 2°C.
(Here is the citation for the coral study: J. Silverman, K. Schneider, D.I. Kline, T. Rivlin, A. Rivlin, S. Hamylton, B. Lazar, J. Erez, K. Caldeira. Community calcification in Lizard Island, Great Barrier Reef: A 33 year perspective. Geochimica et Cosmochimica Acta, 2014; DOI: 10.1016/j.gca.2014.09.011)
© Jan TenBruggencate 2014

Saturday, September 13, 2014

On the big island, the first honeycreeper hybrid, between the redbirds `i`iwi and `apapane

There is a new native Hawaiian bird in the forest, a cross of two of the brightest jewels of the Island landscape—the red `i`iwi and the red `apapane.

(Image: The first-ever cross between an `i`iwi and `apapane. At left an `i`iwi, at right an `apapane, and at center the hybrid. All photos by Olga Lansdorp, courtesy of the authors.)
The unusual bird was caught in 2011 in the Upper Waiakea Forest Reserve on Hawai`i Island, and released after being banded. A DNA analysis performed on a single feather taken from the bird confirmed that it was the first-known cross of the two native honeycreepers.

A study on the find was published in the Wilson Journal of Ornithology by authors Jessie Knowlton of the Michigan Technological University and the Smithsonian Conservation Biology Institute, David Flashpohler of Michigan Technological University, and Rotzel Mcinerney and Robert Fleischer, both of Smithsonian Conservation Biology Institute. (The Wilson Journal of Ornithology 126(3):562–568, 2014)

The paper is entitled, “First Record of Hybridization in the Hawaiian Honeycreepers: `I`iwi (Vestiaria coccinea) x `Apapane (Himatione sanguinea).” The abstract is here.

Two key questions, of course, are opposite sides of the investigation: How did this happen, and why didn’t this happen before? With Darwin’s Galapagos finches, such crosses between species are known to occur. In Hawai`i, until now, they have not been known to happen.

“Our discovery is important in light of recent evidence that introgression and hybridization play important roles in speciation, maintenance of genetic diversity, and the movement of advantageous alleles within and between species,” the authors write.

DNA testing found that the bird’s mother was an `i`iwi and the father was the `apapane. 

The bird looked a little like both parents. Its size was closer to that of a male `apapane. Its color, based on a photograph with the paper, seems intermediate between the bright red of the `apapane and the orange-red of the `i`iwi. 

But its bill showed the combination most clearly. The `i`iwi has a long, curved, orange-colored bill. The `apapane has a short, black bill. The hybrid bird has a longish, curved bill about halfway between the lengths of the parent bills, and black in color.

The bird is a male, and the analysis could not determine whether the it was capable of reproducing. 

“This individual is the first hybrid ever confirmed for Hawaiian honeycreepers, despite ongoing study of these species for (more than) 40 years with thousands of individuals captured and banded and many thousands of specimens collected for museums,” the authors write.

Hawaiian honeycreepers are all believed to have evolved from a single parent bird, developing into an amazing range of colors, beak types, food preferences and habitat requirements. The `i`iwi and `apapane, then, are very distant cousins—genetic work suggested the species diverged from each other 1.6 million years ago. 

And they are different in a number of ways that argue against genetic crossing.

“The circumstances that gave rise to a mating between a female `i`iwi and a male `apapane are difficult to imagine. `I`iwi are aggressive and socially dominant to `apapane, and the average bill length of `i`iwi is more than 10 mm greater than `apapane. Further, `i`iwi are larger than `apapane, and it is unusual for a female of a larger species to choose to mate with a male of a smaller species,” the authors write.

On the other hand, they are perhaps the most likely honeycreepers to cross.

“`Apapane and `i`iwi are more similar in courtship behavior to each other than with other honeycreeper species and have overlapping breeding seasons,” Knowlton and the team write.

In the forest area where the hybrid bird was found, `i`iwi are about a quarter as common as `apapane. Avian malaria is hitting hard the vulnerable `i`iwi populations, while `apapane, while also impacted, show some resistance to the disease. 

One of the things that isn’t known is whether there might be other such crosses, or whether this bird was able to reproduce. If so, there might be birds in the Upper Waiakea Forest Reserve that are ¾ `i`iwi and `1/4 `apapane, or the reverse.

That’s potentially interesting, because disease-resistant crosses could preserve DNA from the emblematic Hawaiian redbirds.

There is still plenty of mystery in this story. The hybrid bird, known only by its band number of 2551-51657, was released back into the wild after being banded, and has never been seen again.

© Jan TenBruggencate 2014

Monday, September 8, 2014

Polynesian navigation: Robust, varied.

Smithsonian Institution geographer Doug Herman, who is following Hokule`a’s voyage around the world, has written a fine summary on recent thinking about Polynesian navigation.

The essence of the piece recalls that in the mid-1900s, standard thought was that early Polynesians could not have had the capacity to navigate long distances, to sail into the wind, and that the population of the Pacific islands could be explained by accidental drift voyages.

(Image: Hokule`a sailing in the rain during a voyage through the Northwestern Hawaiian Islands. Credit: Jan TenBruggencate)

This theory ignored clear indications in the oral traditions of Pacific peoples, which review repeated back-and-forth voyages. Even Capt. James Cook in the late 1700s knew Polynesians had done the hard work of active discovery. So did many of the researchers of the late 1800s and early 1900s, including the great Maori scholar, Te Rangi Hiroa.

But in 1947 an extremely popular voyage by Thor Heyerdahl reset popular thinking. Heyerdahl argued that Polynesians had simply drifted from island to island. And he built a balsa raft that drifted from South America to the eastern Pacific islands of the Tuamotu to show it was possible.

It includes the great 1983 video “The Navigators, Pathfinders of the Pacific” on navigation, Hokule`a’s first voyage, and Satawal navigator Mau Piailug. The video additionally has fascinating imagery of traditional canoe building, rope making and navigation training.

Herman makes the point, as the title suggests, that Thor Heyerdahl and Kon Tiki misrepresented the evidence.

But Herman misses the, perhaps, bigger point—the Hokule`a and David Lewis’s seminal work on Polynesian navigation occurred in large because of Heyerdahl, and his followers, like the dismissive Australian Andrew Sharp, who denigrated Polynesian skills and intellect.

Were it not for the naysayers, would Hawaiians have risked their lives to prove that their voyaging ancestors could and did navigate? 

Modern research proves not only that they could, but that they did, and that their navigational skills were not only robust but quite varied. 

Mau Piailug and Satawal navigators used  a star compass. Chief Kaveia and the Duff Island navigators of the Solomons use a wind compass and mysterious lights in the water called Te Lapa, as described by anthropologistMimi George. Modern navigator Nainoa Thompson uses still a different system ofhis own.

Different tools. Same result. Another proof. 

© Jan TenBruggencate 2014

Thursday, September 4, 2014

A fungus for all seasons: causes dandruff in humans, but afflicts lobsters, sponges and corals as well

A fungus responsible for skin diseases in humans is also turning out to be common in the marine environment, and in combination with warming oceans is implicated in coral disease.

University of Hawai`i botanist Anthony Amend reported on the endlessly adaptable fungus Malassezia in the August 21, 2014, issue of the scientific journal PLOS Pathogens.

 It turns out the various species of Malassezia are everywhere, including some of the most inhospitable climates on the planet, from icy arctic soils to hot deep sea vents. That’s a far wider range of habitats than anyone had previously recognized. Until now, they have been understood as a land-based mammal problem.

It has been associated with dandruff, eczema and other human skin ailments, and it’s on seals as well. But Amend’s genetic studies of samples of diverse marine creature tissues show it has a much larger host population. It has now also linked to skin disease in lobsters, fish, plankton, and, yes, corals.

“Studies of fungi from environmental samples show that Malassezia are exceedingly widespread and ecologically diverse. Recent studies in little-characterized marine environments point to extensive diversification of Malassezia-like organisms, providing exciting opportunities to explore the ecology, evolution and diversity of this enigmatic group,” Amend wrote in the paper.

Bizarrely, a single strain has been found both in the arctic cold and in hydrothermal deep sea vents. 

“We have found multiple new examples of these fungi on corals, sponges and algae, and in water samples, deep sea thermal vents and sediments from Hawai‘i and around the world,” Amend said in a University of Hawai`i press release.

And the genetic work suggests the fungus repeatedly evolved from the marine environment to land and back again. The kinds that cause itching in humans are genetically intermediate between some of the marine species.

At Palmyra Atoll, to the south of Hawai`i, Amend found a tight link between Malassezia and a disease of coralline algae, which increased when water got warmer. That’s of interest to the Islands in a time of climate change, since coralline algae are a dominant builder of Hawai`i’s protective reef structures.

“A study of crustose coralline algae around Palmyra Atoll found that a Malassezia phylotype was abundant in banding disease lesions. Incidence of the disease increased by an order of magnitude following an el Niño event. A laboratory manipulation study showed that disease virulence correlated with an interaction between increases in CO2 and temperature,” the paper said.

It is not yet clear whether the fungus is the cause of the coral banding disease, or simply occupied a weakened reef.

“Analysis of environmental sequences demonstrates that putative members of the Malassezia lineage likely rank among the most widespread fungi on the planet,” Amend wrote. 

© Jan TenBruggencate 2014