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04.09.2024 - 14:20 [ frontiersin.org ]

When and Why Did Human Brains Decrease in Size? A New Change-Point Analysis and Insights From Brain Evolution in Ants

(22 October 2021)

But we also find that human brain size reduction was surprisingly recent, occurring in the last 3,000 years. Our dating does not support hypotheses concerning brain size reduction as a by-product of body size reduction, a result of a shift to an agricultural diet, or a consequence of self-domestication. We suggest our analysis supports the hypothesis that the recent decrease in brain size may instead result from the externalization of knowledge and advantages of group-level decision-making due in part to the advent of social systems of distributed cognition and the storage and sharing of information. Humans live in social groups in which multiple brains contribute to the emergence of collective intelligence. Although difficult to study in the deep history of Homo, the impacts of group size, social organization, collective intelligence and other potential selective forces on brain evolution can be elucidated using ants as models.

04.09.2024 - 13:15 [ Welt.de ]

Evolution: Das ist der Grund, wieso die Gehirne der Menschen schrumpfen

(16.11.2021)

Dass unser Gehirn langsam etwas an Masse verloren hat, ist jedoch nicht ganz so lange her: Erst vor rund 3.000 Jahren begann es zu schrumpfen.

(…)

Die Art und Weise, wie sich Individuen in einem Ameisenstaat organisieren, ähnelt unseren modernen Gesellschaftsstrukturen. Die Insekten haben, verglichen mit ihrer Körpergröße, ein Mini-Gehirn. Es ist etwa eine Million Mal kleiner als das eines Menschen – sie können aber Großes leisten. Das Prinzip dahinter ist eine Art kollektive Intelligenz. Nicht jeder muss alles können oder wissen, es gibt eine klare Aufgabenteilung.

26.04.2024 - 02:35 [ Smithsonian Magazine ]

An Evolutionary Timeline of Homo Sapiens

(February 2, 2021)

Neanderthals once stretched across Eurasia from Portugal and the British Isles to Siberia. As Homo sapiens became more prevalent across these areas the Neanderthals faded in their turn, being generally consigned to history by some 40,000 years ago. (…)

Despite the bits of genetic ancestry they contributed to living people, all of our close relatives eventually died out, leaving Homo sapiens as the only human species. Their extinctions add one more intriguing, perhaps unanswerable question to the story of our evolution—why were we the only humans to survive?

26.04.2024 - 02:05 [ Science.org ]

A global environmental crisis 42,000 years ago

(19 Feb 2021)

Do terrestrial geomagnetic field reversals have an effect on Earth‘s climate? Cooper et al. created a precisely dated radiocarbon record around the time of the Laschamps geomagnetic reversal about 41,000 years ago from the rings of New Zealand swamp kauri trees. This record reveals a substantial increase in the carbon-14 content of the atmosphere culminating during the period of weakening magnetic field strength preceding the polarity switch. The authors modeled the consequences of this event and concluded that the geomagnetic field minimum caused substantial changes in atmospheric ozone concentration that drove synchronous global climate and environmental shifts.

(…)

We precisely characterize the geomagnetic reversal and perform global chemistry-climate modeling and detailed radiocarbon dating of paleoenvironmental records to investigate impacts. We find that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record.

(…)

In addition, chronological uncertainties are complicated in radiocarbon-dated terrestrial and marine records around the Laschamps because of the elevated production of C and Be, cosmogenic radionuclides resulting from the substantial increase in high-energy cosmic radiation reaching the upper atmosphere. The high Be flux has been well described from Greenland and Antarctic ice core records (6, 20, 21), which reveal synchronous century-long Be peaks across the Laschamps that appear to reflect a series of pronounced Grand Solar Minima (GSM; prolonged periods of low solar activity similar to the Spörer and Maunder Minima: 1410 to 1540 CE and 1645 to 1715 CE), with unknown climate impacts (20, 21).

26.04.2024 - 01:50 [ ScienceNews.org ]

50 years ago, scientists named Earth’s magnetic field as a suspect in extinctions

(November 19, 2020)

Effects of Earth’s magnetic field — Science News, November 21, 1970

„Earth’s magnetic field has frequently reversed at intervals of 1 million to 100 million years. A few scientists now suspect that these reversals may have had drastic effects on terrestrial life.… During the past 2.5 million years, eight species of one-cell marine animals called Radiolaria became extinct. Six of these extinctions occurred simultaneously throughout their geographic range immediately following magnetic reversals.“

26.04.2024 - 01:30 [ PRI.org ]

Scientists link Earth’s magnetic reversals to changes in planet’s life and climate

(April 19, 2021)

The researchers examined the rings of the tree to look for changes in the amount of carbon-14 over a period of years, Gramling explains. Carbon-14 is useful not only for dating things, but because the interaction of cosmic rays with molecules in the atmosphere produces a lot of it. And when the Earth has a weakened magnetic field, more cosmic rays hit the planet.

The scientists indeed found a large spike in carbon-14 in the tree, which they could then compare with the rock record that indicated a magnetic reversal. (…)

In addition, there is the documented rise in cave art right about 41,000-42,000 years ago, Gramling points out.

20.09.2023 - 03:12 [ Wikipedia ]

1000 Genomes Project

Some genomic differences may not affect fitness. Neutral variation, previously thought to be “junk” DNA, is unaffected by natural selection resulting in higher genetic variation at such sites when compared to sites where variation does influence fitness.[14]

It is not fully clear how natural selection has shaped population differences; however, genetic candidate regions under selection have been identified recently. (…)

It was found that on average, each person carries around 250–300 loss-of-function variants in annotated genes and 50-100 variants previously implicated in inherited disorders. Based on the two trios, it is estimated that the rate of de novo germline mutation is approximately 10−8 per base per generation.

20.09.2023 - 02:51 [ National Library of Medicine / National Institutes of Health (NIH) ]

The 1000 Genomes Project: Welcome to a New World

(Dec 2015)

“Now this is not the end… But it is, perhaps, the end of the beginning” as Winston Churchill said. Large-scale sequencing projects will continue for more regional or ethnic groups, in order to extend the global coverage. Much effort will focus on a better understanding of the relationship between genetic variation and common disorders. The translation of this massive genetic information to human health will benefit from the development of complex databases gathering genetic, clinical, and biological data, such as multi-omics profiles, while maintaining protection of potentially sensitive personal information (3). Efforts are also underway to increase genetic awareness in the public and to educate health professionals

24.04.2023 - 13:21 [ Science.org ]

A global environmental crisis 42,000 years ago

(19 Feb 2021)

Do terrestrial geomagnetic field reversals have an effect on Earth‘s climate? Cooper et al. created a precisely dated radiocarbon record around the time of the Laschamps geomagnetic reversal about 41,000 years ago from the rings of New Zealand swamp kauri trees. This record reveals a substantial increase in the carbon-14 content of the atmosphere culminating during the period of weakening magnetic field strength preceding the polarity switch. The authors modeled the consequences of this event and concluded that the geomagnetic field minimum caused substantial changes in atmospheric ozone concentration that drove synchronous global climate and environmental shifts.

(…)

We precisely characterize the geomagnetic reversal and perform global chemistry-climate modeling and detailed radiocarbon dating of paleoenvironmental records to investigate impacts. We find that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record.

24.04.2023 - 13:16 [ ORF.at ]

Erdmagnetfeld: Polwanderung veränderte das Weltklima

Ungefilterte Strahlung aus dem Weltraum zerriss Luftpartikel in der Erdatmosphäre, trennte Elektronen ab und emittierte Licht. Diese ionisierte Luft brutzelte die Ozonschicht weg, heißt es in einer Presseaussendung zur Studie. In Folge dürften überall auf dem Globus Polarlichter aufgetaucht sein, nicht nur rund um den geographischen Nord- und Südpol wie heute. (…)

Das Erdmagnetfeld schwächelt bereits seit rund 2.000 Jahren wieder. Verglichen mit den ersten direkten Messungen vor 170 Jahren wurde eine Abschwächung um neun Prozent festgestellt, im Bereich des Südatlantiks sogar um dreißig Prozent.

25.10.2021 - 17:04 [ PRI.org ]

Scientists link Earth‘s magnetic reversals to changes in planet‘s life and climate

(April 19, 2021)

The researchers examined the rings of the tree to look for changes in the amount of carbon-14 over a period of years, Gramling explains. Carbon-14 is useful not only for dating things, but because the interaction of cosmic rays with molecules in the atmosphere produces a lot of it. And when the Earth has a weakened magnetic field, more cosmic rays hit the planet.

The scientists indeed found a large spike in carbon-14 in the tree, which they could then compare with the rock record that indicated a magnetic reversal. (…)

In addition, there is the documented rise in cave art right about 41,000-42,000 years ago, Gramling points out.

20.09.2021 - 05:45 [ PRI.org ]

Scientists link Earth‘s magnetic reversals to changes in planet‘s life and climate

(April 19, 2021)

The researchers examined the rings of the tree to look for changes in the amount of carbon-14 over a period of years, Gramling explains. Carbon-14 is useful not only for dating things, but because the interaction of cosmic rays with molecules in the atmosphere produces a lot of it. And when the Earth has a weakened magnetic field, more cosmic rays hit the planet.

The scientists indeed found a large spike in carbon-14 in the tree, which they could then compare with the rock record that indicated a magnetic reversal. (…)

In addition, there is the documented rise in cave art right about 41,000-42,000 years ago, Gramling points out.

21.02.2021 - 13:30 [ Sciencealert.com ]

Earth‘s Magnetic Field Could Be Changing Much Faster Than We Ever Realised

(08.07.2020)

Quicker changes in direction seem to coincide with a local weakening of the magnetic field, the new research found. One shift in particular was highlighted: a movement of 2.5 degrees per year 39,000 years ago, right after the most recent Laschamp excursion flip, when the Earth‘s magnetic field was weakened around the west coast of Central America.

21.02.2021 - 13:05 [ ScienceNews.org ]

50 years ago, scientists named Earth’s magnetic field as a suspect in extinctions

(November 19, 2020)

Effects of Earth’s magnetic field — Science News, November 21, 1970

„Earth’s magnetic field has frequently reversed at intervals of 1 million to 100 million years. A few scientists now suspect that these reversals may have had drastic effects on terrestrial life.… During the past 2.5 million years, eight species of one-cell marine animals called Radiolaria became extinct. Six of these extinctions occurred simultaneously throughout their geographic range immediately following magnetic reversals.“

21.02.2021 - 12:40 [ Science Magazine ]

A global environmental crisis 42,000 years ago

(19.02.2021)

We find that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record.

21.02.2021 - 12:35 [ CNN ]

Reversal of Earth‘s magnetic poles may have triggered Neanderthal extinction — and it could happen again

(19.02.2021)

Some 42,000 years ago, in an event known as the Laschamp Excursion, the poles did just that for around 800 years, before swapping back — but scientists were unsure exactly how or if it impacted the world.

Now, a team of researchers from Sydney‘s University of New South Wales and the South Australian Museum say the flip, along with changing solar winds, could have triggered an array of dramatic climate shifts leading to environmental change and mass extinctions.

22.01.2020 - 22:02 [ Dr. Jessie Christiansen ‏/ Twitter ]

I have always been interested in galactic archaeology, but I don‘t think this is what they meant. Did you know that dinosaurs lived on the other side of the Galaxy?

(28.08.2019)

02.01.2020 - 16:57 [ Dr. Jessie Christiansen ‏/ Twitter ]

I have always been interested in galactic archaeology, but I don‘t think this is what they meant. Did you know that dinosaurs lived on the other side of the Galaxy?

(28.08.2019)

15.11.2019 - 15:00 [ businessinsider.fr ]

A NASA scientist‘s incredible animation shows how dinosaurs roamed the Earth on the other side of the Milky Way galaxy

Our sun orbits the galaxy‘s center, so many dinosaurs roamed the Earth while the planet was on the other side of the Milky Way.

Our solar system‘s orbit keeps us just the right distance from the galaxy‘s chaotic center for life to exist.

15.11.2019 - 12:27 [ Dr. Jessie Christiansen ‏/ Twitter ]

I have always been interested in galactic archaeology, but I don‘t think this is what they meant. Did you know that dinosaurs lived on the other side of the Galaxy?

30.05.2019 - 16:11 [ arxiv.org ]

Hypothesis: Muon Radiation Dose and Marine Megafaunal Extinction at the end-Pliocene Supernova

(November 2018)

Considerable data and analysis support the detection of one or more supernovae (SNe) at a distance of about 50 pc, ∼2.6 million years ago. This is possibly related to the extinction event around that time and is a member of a series of explosions that formed the Local Bubble in the interstellar medium. We build on previous work, and propagate the muon flux from SN-initiated cosmic rays from the surface to the depths of the ocean. We find that the radiation dose from the muons will exceed the total present surface dose from all sources at depths up to 1 km and will persist for at least the lifetime of marine megafauna. It is reasonable to hypothesize that this increase in radiation load may have contributed to a newly documented marine megafaunal extinction at that time.

30.05.2019 - 15:55 [ New York Times ]

STUDY HINTS EXTINCTIONS STRIKE IN SET INTERVALS

(11. Dezember 1983)

At a conference on mass extinctions, held in August at Northern Arizona University in Flagstaff, Dr. Sepkoski said the timing of these events suggested that “there is indeed a statistically significant periodicity in the observed distribution of events of mass or accelerated extinction over the last 250 million years.“ Search for Answers

He confessed this “stumped“ him and Dr. Raup, saying: “We are aware of no documented process with a cycling time approximately 26 million years. But with that long a cycle, we suspect that the forcing agent will not be terrestrial but rather solar or galactic.“

30.05.2019 - 15:49 [ Harvard.edu ]

Cosmic-ray volleys from the Galactic Center and their recent impact on the earth environment

Authors: Laviolette, P. A.
Journal: Earth, Moon, and Planets (ISSN 0167-9295), vol. 37, March 1987, p. 241-286.

29.01.2015 - 05:15 [ Physics.aps.org ]

Focus: Gamma-Ray Bursts Determine Potential Locations for Life

The researchers found that there was a 60% chance we were hit in the past 1 billion years or a 90% chance if one looks back 5 billion years—consistent with previous estimates based on preliminary models of GRBs. It’s possible, then, that a nearby GRB could have caused one of the mass extinctions recorded in the fossil record. In fact, the Ordovician extinction, which occurred around 440 million years ago, had certain signatures of a GRB-induced event, such as a greater extinction rate among surface-dwelling marine life as compared with bottom-dwellers