In the Beginning There was Proto-Earth and Theia

4.6 billion years ago, gravitational forces pulled enough star dust and rock together to form the planet Proto-Earth, and it began to orbit the sun, but another planet–Theia–shared the same orbit for 20-30 million years. According to the Giant Impact Hypothesis, the shared orbit eventually led to a collision between these 2 planets. Ejecta from the impact circled the Earth’s orbit for millions of years in a ring not unlike the ring that currently circles Saturn. Gravity consolidated the ring into the moon which had a much closer orbit then than it does today.

20-30 million years after Proto-Earth formed it was struck by another planet that occupied the same orbit.

The impact of the collision between Proto-Earth and Theia caused ejecta to orbit earth in a ring. This ring eventually consolidated into the moon.

Convincing evidence supports the Giant Impact Hypothesis. Earth’s spin and the moon’s orbit have similar orientations. Earth’s high momentum of rotation suggests the occurrence of an ancient impact. Analysis of moon dust indicates it was once molten–the result of a fiery impact that melted the ejecta that eventually accreted to form the moon. (Scientists refer to the consolidation of material into a planet as accretion.) The moon has a small core, suggesting most of Theia’s core fused with Proto-Earth’s core. The moon has small quantities of volatile elements, indicating most vaporized upon impact. Isotope ratios of zinc and oxygen on the moon are identical with those on Earth.

This is what the early Earth looked like after the moon consolidated. Widespread tectonic activity combined hydrogen and oxygen in rocks into water vapor released by volcanoes.

Earth is the most unusual planet in the solar system, and from what scientists can determine is unlike any known planet from other solar systems based on the limited data they can glean from such distant bodies. Water is abundant on Earth, while most planets are absolute deserts. Moreover, Earth is surrounded by an oxygen-rich atmosphere. Scientists wonder how earth accumulated water because they believe heat from the early sun was so great that most of the water on Proto-Earth boiled off. The prevailing theory posits meteorites and/or comets from the outer solar system delivered water to earth. However, a new study suggests water always existed in earth’s rocks. Scientists examined 13 inner orbit meteorites, known as enstatite chondrite meteorites, and determined they have the same isotopic ratios of various elements, including hydrogen, found in rocks on earth. Hydrogen and oxygen in earth rocks combined to form water that was released as vapor during volcanic activity. Proto-Earth likely formed from the accretion of enstatite chondrite meteors and asteroids within just a 5-million-year timespan. It’s mind-boggling to imagine how the consolidation of lifeless rocks led to our weird planet rife with so many different lifeforms.

Reference:

Piani, L.; et. al.

“Earth’s Water may have been Inherited from Material Similar to Enstatite Chondrite Meterorites”

Science 369 (6907) August 2020

Schiller, M.; M. Bizzarro, and J. Siebert

“Iron Isotope Evidence for very Rapid Accretion and Differentiation of the Proto-Earth”

Science Advances 6 (7) 2020

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What Vultures Eat in Coastal South Carolina

A road trip along any highway in Georgia will usually reward birdwatchers with the sight of vultures patrolling the skies above it. They feast upon the carnage caused by vehicles colliding into animals. Without vultures, roads would be littered with rotting corpses, attracting a plague of disease-carrying flies. In India recently, vultures were poisoned, causing a disastrous problem with sanitation. There are 2 species of vultures in southeastern North America–the turkey vulture (Cathartes aura) and the black vulture (Coragyps atratus). Both species nest communally, but the former flies in solitary pursuit of carrion, while the latter scavenges in flocks for dead animals. Though carrion makes up a majority of the diet of turkey vultures, they are also known to feed upon fruit and insects. Black vultures have an even more varied diet and will eat eggs, nestlings, newborn mammals, fish, fruit, and shit. They will actually peck out the eyes of newborn calves that then go into shock and die, providing a feast for the birds.

Scientists studying vulture diets in coastal South Carolina examined 176 pellets found under communal roosts of vultures. The 3 most common animal remains found in these pellets included in order white-tailed deer, striped skunk, and raccoon. Human garbage was found in 45% of the pellets. Vultures in this region basically live on roadkill and garbage.

Black vultures scavenging a road-killed cat in Augusta, Georgia.

Vulture populations in North America have likely increased over the past 2 centuries because the increasing population of humans has provided them with such an abundance of food. They are uniquely evolved to consume rotting flesh without ill effects and are able to take advantage of the carrion supply resulting from the habits of humans. They have heads and necks naked of feathers, so blood and gore doesn’t accumulate on them, and they are resistant to bacteria toxic to most other animals. However, they do prefer fresher meat. They nest on the ground, and all they need is a thicket where they can hide their eggs and young. They can live for decades.

Vultures may have been just as common or perhaps more so during the Pleistocene when they scavenged the corpses of megafauna. There were a greater variety of species then. The 2 species that live today occurred then, though some scientists consider the Pleistocene black vulture (Coragyps occidentalis) to be a different species. It was on average larger but otherwise identical to the modern species. In addition, massive teratorns that likely tore open freshly deceased mammoths and ground sloths soared in the sky. 2 species similar to Old World vultures ranged into parts of North America. Fossils of the American griffin vulture and another species have been found in southwestern North America, and they may have ranged into other regions of the continent. New World vultures, the black vultures and turkey vultures, were formerly thought to be more closely related to storks, but genetic studies determined they are most closely related to ospreys and secretary birds. Old World vultures belong in the family that includes eagles, kites, and hawks.

Refererence:

Hill, J., et. al.

“Diets of Black Vultures and Turkey Vultures in Coastal South Carolina, USA with a Review of Species Dietary Information”

Southeastern Naturalist 21 (1) 2022

Breasts were Invisible in Hollywood Movies until the 1940s

I like to watch old movies on Turner Classic. I often joke with my wife that boobs weren’t invented until the 1940’s because silent movie actresses whose careers continued until well into the 1930’s talkie era were flat-chested. I google-searched images of silent movie actresses and confirmed the 56 most famous actresses before World War II wore A-cup bras. Occasionally, little-known actresses with big or at least medium-sized breasts were given bit parts in early movies, but they invariably played maids or matronly figures unimportant to the script. 19th century literature portrayed the ideal woman most desired by men as frail and sickly. Men supposedly pined over helpless women on the verge of their death beds. Love was associated with sadness and a sense of loss. I wonder if this notion influenced early 20th century cinema. Most people were poor, and plenty were malnourished back then, perhaps contributing to smaller average breasts sizes. Maybe, there were simply more flat-chested actresses available for work during this time period.

Clara Bow, a famous silent movie star. The 56 most successful actresses of the silent era and early talkies were all flat-chested.

During World War II America was flexing its muscles, and Americans were becoming more prosperous. Hollywood finally started featuring healthy-looking voluptuous actresses. Howard Hughes produced a western (The Outlaw) that prominently featured Jane Russell’s cleavage. The film, released during 1943, broke barriers and defied censors. Voluptuous women including Marilyn Monroe, Kim Novak, and Elizabeth Taylor began to take center stage as the baby boom exploded. Macho war veterans came home from service and impregnated their Mrs. America wives. Women with 36-24-36 figures were the ideal–the opposite of the frail damsels-in-distress so sought after during the previous era.

Jane Russell was the first Hollywood star with big boobs. Howard Hughes featured her breasts prominently in his epic Western, The Outlaw.

Iconic photo of Sophia Loren eyeing Jane Mansfield’s tits. Mansfield was the first actress to perform nude in a mainstream Hollywood movie. Stag movies featuring nude women were among the first films ever made, but they were not distributed to mainstream audiences.

The 1960’s and 1970’s saw a trend of skinny actresses, but full-figured women were no longer completely absent, and they eventually returned to popularity. Even lean actresses rejected the flat-chested look and often chose to have surgically enhanced breasts. A great majority of mainstream actresses have frequent plastic surgery, and porn actresses seek ever-expanding cleavages. There seems to be no limit to how large they will go. I prefer naturally large breasts.

Modern actress Christina Hendricks with her ex-husband Geoffrey Arend. She probably has the largest breasts in Hollywood history. They make Jane Mansfield’s look small. Breasts are modified sweat glands found on all mammals, including the primitive egg-laying monotremes. Wow! Those are some modified sweat glands.

Surprisingly, there are few scientific studies of breasts and culture. The United States is tied with the United Kingdom, Iceland, Norway, and Luxembourg for largest average bra size; but the claim that Americans have the biggest boobs in the world was a hoax. A few years ago, 18 media outlets from The New York Daily Times to Teen Magazine reported a find by The Journal of Female Health Science that Americans had the biggest average boobs in the world. This journal doesn’t exist. I did find 1 scientific study that surveyed men from Brazil, Cameroon, Namibia, and Czechoslovakia on their breast size preference. Most men from those countries preferred medium-sized breasts. Not me. I favor the biggest breasts and the fattest asses. I told my wife, if I outlive her, I will replace her with a sex doll. (Amazon.com sells realistic, voluptuous, life-size sex dolls for a few hundred dollars.) I have gotten particular in my old age, and if a real woman wanted sex with me, she would have to make a minimum weight limit. She would have to weigh at least 170 pounds. I have been making love to a heavyset woman for 30 years, and I am too old to change.

Happy Valentines Day

Reference:

Havlicek, J. et. al.

“Men’s Preference for Women’s Breast Size and Shape in 4 Cultures”

Evolution and Human Behavior 38 (2) 2017

Some Pleistocene Megafauna may have Survived in the Yukon until the Mid-Holocene

One of the first entries I wrote for this blog over 10 years ago highlighted a study of seda-DNA (short for sediment DNA) from cores taken in Alaskan permafrost. Permafrost preserves DNA of local animals that were shedding hairs, urinating, and defecating on the landscape. Different levels of the core were radio-carbon-dated, and scientists came to a surprising conclusion–mammoths and horses survived thousands of years after the youngest known sub-fossil evidence. Mammoths lived on mainland Alaska until 9700 years BP, and horses survived there until 7000 years ago. Recently, some of the same scientists conducted a similar study in the Klondike region of the Yukon, and they came to a similar conclusion. This study of 4 sites in the region was more extensive and also kept track of plant DNA, so changes in the environment could be detected. Apparently, mammoth, horses, and bison persisted in small refugial populations in the region thousands of years after the youngest known dated specimens in the paleontological record. They call this a temporal ghost range. They detected a DNA signal of these extinct and extirpated species from 9200 years BP to 5700 years BP, while paleontological evidence indicated they had disappeared from the region ~12,000 years ago. The authors of this study concede older sediment could have mixed with younger sediment, causing a mistaken observation, but they think this is unlikely because the samples were the same from 21 different cores taken from 3 different sites, and changes in plant composition were consistent with what they expected from unmixed sediment.

Chart showing temporal abundance of megafauna and shifts in climate. From the below reference.

Chart showing abundance of seda-DNA of plants and animals from 4 permafrost core sites in the Yukon. Most species of megafauna were more abundant when grassy steppe was widespread, but they seem to have still occurred in refugial populations long after the shift from grassy steppe to more mesic shrub and forest habitat. Also from the below reference.

Scientists hoped the study could shed light on why the grassy steppe ecosystem of the Late Pleistocene collapsed. There are 2 schools of thought. Dr. Guthrie believes increased precipitation and cloud cover brought on by climate change changed the environment from grassy steppe to mesic peat marsh, willow scrub, and spruce forest; thus, depriving grass-eating animals of their primary food source and causing their extinction or extirpation. Dr. Zimov believes the disappearance of the megafauna itself caused the transformation of the landscape. He thinks herds of large animals trampling, grazing, and defecating suppressed woody growth and maintained the grasslands. Humans overhunted megafauna into extinction in this scenario.

Data from this study can be used to support both arguments. The biggest decline in mammoth populations occurred about 20,000 years ago–long before the transformation of the mammoth steppe into present day environments. There is ephemeral archaeological evidence of people in North America then, and they might have started reducing mammoth herds. Also, mammoths, horses and bison declined about the same time Homo sapiens became more common. However, the final significant decline in megafauna populations did occur when the grassy mammoth steppe was in transition to a landscape dominated by woody vegetation.

I’ve long been convinced humans are completely responsible for the extinction of most, if not all, Pleistocene megafauna, even in this remote region. I think populations of grazing megafauna did decline in this region due to changes in climate. But grassy environments never completely disappeared, and in some areas these refuges were still capable of supporting smaller populations of grazers which did maintain small grasslands with their activities. These refugial populations could have expanded to repopulate the region given favorable changes in climate, like those that occurred periodically throughout the Pleistocene. However, man wiped out these interglacial refugial populations of mammoths, bison, and horses. If not for man, I think there still would be local populations of these species in the region, but they just wouldn’t be as abundant as they were during Ice Ages. They were not picky feeders and could subsist on some woody vegetation. Incidentally, there is fossil evidence of steppe bison (Bison antiquus) from central Canada (not exactly in the region but not on the other side of the continent either), dating to the mid-Holocene. See:

A Pleistocene Species of Bison (Bison antiquus) Survived in Canada until 4830 Calender Years Ago

Reference:

Murchie, T. et. al.

“Collapse of the Mammoth Steppe in Central Yukon as Revealed by Ancient Environmental DNA”

Nature Communications Dec 2021

https://www.nature.com/articles/s41467-021-27439-6