El ADN revela secretos de la primera migración a América

Dos estudios genéticos separados hallaron evidencias de un sorprendente vínculo genético entre las poblaciones nativas de las Américas y Oceanía.

El ADN de algunos nativos amazónicos muestra una semejanza significativa con los habitantes indígenas de Australia y Melanesia, el cinturón de islas que van desde el Pacífico occidental hasta Fiji.

Los dos grupos de investigación, sin embargo, hacen distintas interpretaciones de cómo fue poblada América.

Los estudios fueron publicados en las revistas Science y Nature.

Hay un consenso en que los primeros pobladores de las Américas llegaron a través de Siberia, por un puente de tierra que conectaba con Europa y Asia.

Pero no hay acuerdo sobre la procedencia de estos pobladores y en qué momento llegaron.

Al analizar el ADN de los nativos americanos modernos y de antiguos restos humanos, el grupo que escribe para Science concluye que todos los nativos americanos de la actualidad proceden de una migración única no más temprana a hace más de 23.000 años.

Entonces, alegan, hace unos 13.000 años los nativos americanos se dividieron en dos ramas: una que ahora está dispersa por América del Norte y del Sur, mientras que la otra se limita a América del Norte.

"Nuestro estudio muestra que el modelo más simple posible parece ser verdadero, con una sola y notoria excepción", le dijo a la BBC el profesor Rasmus Nielsen de la Universidad de California, Berkley.

No hay acuerdo sobre la procedencia de los pobladores de América y en qué momento llegaron.

"Así que las ideas fantasiosas de que de alguna manera América fue poblada por personas procedentes de Europa y todo tipo de lugares son erróneas".

El análisis también descarta la teoría, defendida por algunos, de una migración escalonada desde Siberia: la primera de hace más de 30.000 años que fue detenida durante 15.000 años por el hielo que bloqueaba la ruta y una segunda oleada una vez que el camino se despejó.

Pero, al igual que en el estudio de la revisa Nature, el equipo de Nielsen registró rastros de ancestros "australo-melanesios" en algunas poblaciones, incluidas aquellas de las islas Aleutianas (frente a Alaska) y la comunidad surui del Amazonas brasileño.

El profesor David Reich de la Escuela Médica de Harvard lideró el estudio de Nature.

Reich le explicó a la BBC que "ambos estudios muestran que ha habido múltiples flujos de migración hacia las Américas".

Según Reich, el descubrimiento del linaje oceánicos entre algunos grupos nativos Americanos indica que América fue poblada por una serie de grupos más diversos de lo que anteriormente se creía.

El mapa del artículo de Nature resalta la similitud entre los indígenas amazónicos y los australasianos.

"El modelo más simple posible nunca predijo una afinidad entre los amazónicos y los australasianos", señaló.

"Esto sugiere que hay una población ancestral que cruzó hacia América que es diferente de la población que dio lugar a la gran mayoría de americanos. Y esto es una gran sorpresa".

Reich cree que la explicación más plausible es que hubo una migración separada desde Australasia (región que comprende Australia, Melanesia y Nueva Zelanda), posiblemente hace unos 15.000 años.

Este grupo, considera, probablemente se dispersó más por América del Norte pero gradualmente fue expulsado por otras comunidades nativas americanas.

Por su parte, Nielsen tiene una interpretación diferente pues opina que los rastros del ADN australasiano se derivan de una migración posterior, hace unos 8.000 años, que avanzó por la costa del Pacífico.







El ADN revela secretos de la primera migración a América

Can the U.S. Avoid Chaos In Puerto Rico?

awmakers in Washington appear to be getting increasingly anxious about the situation in Puerto Rico, which is poised to default on some $70 billion in debt the island territory has acquired over the past several years. A key concern is the impact such a default could have on U.S. bond markets.

In a letter to Treasury Secretary Jack Lew on Friday, Senate Finance Committee Chairman Orrin Hatch (R-UT) asked the administration about its plans for dealing with the island’s finances, including its opinion on a move being pushed in Congress to allow Puerto Rico’s municipalities and public utilities to file for Chapter 9 bankruptcy. Hatch’s letter came just days after two other senators, Chuck Schumer (D-NY) and Richard Blumenthal (D-CT) introduced legislation that would make those Chapter 9 filings possible.

Related: How the U.S. Is Helping Sink Puerto Rico

Two big questions right now are whether there is significant support in Congress to make such a change to bankruptcy laws and whether any such action can happen quickly enough to avoid what Hatch called a “chaotic resolution” of the crisis.

Puerto Rican municipalities and public utilities were for years allowed to issue “triple tax-free” obligations – meaning that lenders’ earnings were exempt from local, state, and federal taxation. This made Puerto Rican debt an attractive option for investors, whose eagerness to benefit from the tax exemption helped Puerto Rico cover a substantial budget deficit.

But slow economic growth has made it impossible for Puerto Rico to continue servicing its debts while providing basic services to its citizens.

“The debt is not payable,” the Island’s governor, Alejandro Garcia Padilla, warned in an interview with The New York Times last month. “There is no other option. I would love to have an easier option. This is not politics, this is math.”

Related: S&P Cuts Puerto Rico’s Debt Financing Arm, Says Default Certain

This week, with the report that the agency managing the government’s debt failed to make a deposit into a fund used to pay bondholders, the likelihood of default when those payments come due on August 1 seemed higher than ever. In his letter to Lew, Hatch made it plain where he believes the blame for the crisis lies.

“Unfortunately for residents of Puerto Rico, the Commonwealth has made unsustainable government benefit promises that have been papered over for far too long with debt-fueled expenditures which fail to align benefits with underlying economic fundamentals such as productivity, leading to the ultimate prospect of debt default,” he wrote. “Tragically, unsound financial decisions of government officials have led to a sharp rise in outmigration.”

Hatch noted that he believes there is at least some common ground between the White House and his committee on how to deal with the crisis.

Related: How Puerto Rico’s Debt Crisis Could Hurt the GOP

“I believe that the Obama administration may be in agreement with two reasonable principles to apply to the debt difficulties facing Puerto Rico: 1) there shall not be a federal bailout; and 2) orderly resolution of debt defaults are preferred to chaotic resolutions.”

Among other things, he asked for the administration’s specific thoughts on making Chapter 9 bankruptcy available to Puerto Rico’s bond issuers. He noted that a key element could be the “retroactive application” of that eligibility to existing debts – something that would likely anger creditors who could claim that the government is changing the rules in the middle of the game.

But that rule change may be the only way out, according to some in Washington. In introducing the “Puerto Rico Chapter 9 Uniformity Act” earlier this week, Sen. Blumenthal said, ““This measure is vital to prevent a humanitarian and financial catastrophe – a clearly avoidable disaster. Creditors, investors, ordinary citizens, all will be harmed if the Congress fails to act. This measure is not a bailout – involving not a dime of federal funds. It enables an orderly, rational restructuring of debt, instead of a financial free for all and potential free fall.”

Sen. Schumer added, “We can either do the right thing and give Puerto Rico the bankruptcy option it needs and deserves, or we can risk a disaster on the island and billions in bailout payments later.”

By Rob Garver

Can the U.S. Avoid Chaos In Puerto Rico?

Asteroid spotted in Puerto Rico awes scientists for its shape and tremendous speed

The Arecibo Observatory in Puerto Rico has announced that the first detailed images have been obtained of Asteroid 2011 UW158, which show it has a very odd shape and structure, and that it spins at a tremendous speed on its own axis, phenomena that have intrigued scientists.

The images were obtained by scientists at this Puerto Rican observatory - which has the largest, most sensitive single-dish radio telescope in the world - on Tuesday, July 14, when the asteroid passed by at some 6.9 million kilometers (4.3 million miles) from Earth, or nine time the distance from this planet to the moon.

Many of the asteroids observed up to now appear to be numerous small stones weakly held together by gravity, the observatory said in a communique.

However, Asteroid 2011 UW158 has "an odd shape much like an unshelled walnut" and with a diameter of 300 by 600 meters (1,000 by 2,000 feet), almost twice the size of the reflector of this observatory's radio telescope.

The scientists working there were also able to confirm that the asteroid "rotates very rapidly, once every 37 minutes" as in previous optical observations.

While many scientists were watching the historic flight of the New Horizons spacecraft past the dwarf planet Pluto, those at the Arecibo observatory said they were observing this object, very small and much closer, as it passed by Earth.

"We expect that something this big should have been shattered into smaller pieces by collisions with other asteroids over the age of the Solar System. It is interesting that something this large and apparently solid is still around," scientist Patrick Taylor, of the Planetary Studies Department and leader of these observations, said.

He added that this asteroid will pass relatively close to Earth again in the year 2108, but will not represent any danger.







Asteroid spotted in Puerto Rico awes scientists for its shape and tremendous speed

After Hundreds of Years, Astronomers Finally Agree: This Is the Distance From the Earth to the Sun - The Atlantic

The International Astronomical Union drops the mic.

How far away from Earth is the sun? Not just, you know, very, very far, but in terms of an actual, measurable distance? When you're calculating, how do you decide which location on Earth to measure from? How do you decide which spot on the path of Earth's orbit will serve as the focal point for the measurement? How do you account for the sheer size of the sun, for the lengthy reach of its fumes and flames?

The measurable, mean distance -- also known as the astronomical number -- has been a subject of debate among astronomers since the 17th century. The first precise measurement of the Earth/sun divide, Nature notes, was made by the astronomer and engineer Giovanni Cassini in 1672. Cassini, from Paris, compared his measurements of Mars against observations recorded by his colleague Jean Richer, working from French Guiana. Combining their calculations, the astronomers were able to determine a third measurement: the distance between the Earth and the sun. The pair estimated a stretch of 87 million miles -- which is actually pretty close to the value astronomers assume today.

But their measurement wasn't, actually, a number. It was a parallax measurement, a combination of constants used to transform angular measurements into distance. Until the second half of the twentieth century -- until innovations like spacecraft, radar, and lasers gave us the tools to catch up with our ambition -- that approach to measuring the cosmos was the best we had. Until quite recently, if you were to ask an astronomer, "What's the distance between Earth and the sun?" that astronomer would be compelled to reply: "Oh, it's the radius of an unperturbed circular orbit a massless body would revolve about the sun in 2*(pi)/k days (i.e., 365.2568983.... days), where k is defined as the Gaussian constant exactly equal to 0.01720209895."

Oh, right. Of course.

But rocket science just got a little more straightforward. With little fanfare, Nature reports, the International Astronomical Union has redefined the astronomical number, once and for all -- or, at least, once and for now. According to the Union's unanimous vote, here is Earth's official, scientific, and fixed distance from the sun: 149,597,870,700 meters. Approximately 93,000,000 miles.

For astronomers, the change from complexity to fixity will mean a new convenience when they're calculating distances (not to mention explaining those distances to students and non-rocket scientists). It will mean the ability to ditch ad hoc numbers in favor of more uniform calculations. It will mean a measurement that more properly accounts for the general theory of relativity. (A meter in this case is defined as "the distance traveled by light in a vacuum in 1/299,792,458 of a second" -- and since the speed of light is constant, the astronomical unit will no longer depend on an observer's location with the solar system.) The new unit will also more accurately account for the state of the sun, which is slowly losing mass as it radiates energy. (The Gaussian constant is based on solar mass.)

So why did it take so long for the astronomy community to agree on a standard measurement? For, among other things, the same reason this story mentions both meters and miles. Tradition can be its own powerful force, and the widespread use of the old unit -- which has been in place since 1976 -- means that a new one will require changes both minor and sweeping. Calculations are based on the old unit. Computer programs are based on the old unit. Straightforwardness is not without its inconveniences.

But it's also not without its benefits. The astronomical unit serves as a basis for many of the other measures astronomers make as they attempt to understand the universe. The moon, for example, is 0.0026 ± 0.0001 AU from Earth. Venus is 0.72 ± 0.01 AU from the sun. Mars is 1.52 ± 0.04 AU from our host star. Descriptions like that -- particularly for amateurs who want to understand our world as astronomers do -- just got a little more comprehensible. And thus a little more meaningful.

Megan Garber

After Hundreds of Years, Astronomers Finally Agree: This Is the Distance From the Earth to the Sun

More than 7,000 sardines die in Puerto Rico reservoir from lack of water

Almost 7,000 sardines have died over the last two days in a reservoir in northern Puerto Rico due to the drought that has been shrinking the water supply for two months, making this the third massive dying off of this fish species in less than two weeks.

The secretary of the Natural and Environmental Resources Department, Carmen Guerrero Perez, reported the situation Tuesday in a statement that said the fish perished in the Wildlife Refuge of La Plata Reservoir in Toa Alta.

"We ask citizens not to consume or come in contact with these dead fish, since they decompose rapidly and can put their health at risk," Guerrero said.

She recalled that access to the area was closed to the public on July 1 as a security measure because of the instability of the banks of the reservoir and the impossibility of using the boat ramp.

For her part, Wildlife Refuge manager Marinelly Valentin Sivico said that as happened twice before, the mortality was the result of less available dissolved oxygen for aquatic life due to the low level of the reservoir.

Between July 2-3, close to 8,000 sardines died off and a few days later the same disaster was repeated.

"With the reduction of oxygen in the reservoir, the most vulnerable fish are the sardines," Guerrero said.

"The purpose of these fish in the reservoir is precisely to serve and an indicator of water conditions behind our dams, while also providing recreational fishing," she said.



More than 7,000 sardines die in Puerto Rico reservoir from lack of water