Black Moon 2020: What it is (and why you can't see it)

While a full moon refers to the moment when the moon's Earth-facing side is fully illuminated by sunlight, a new moon refers to the moment when the moon's Earth-facing side is fully in shadow. (Unfortunately, that means the Black Moon will be more or less invisible, even if the moon is high in the sky). 

Although "Black Moon" is not an official astronomical term, there are two common definitions for it. Because the lunar calendar almost lines up with Earth's calendar year, there is typically one full moon and one new moon each month. A second full moon in a single calendar month is sometimes called a "Blue Moon." By this definition, a Black Moon is the flip side of a Blue Moon: the second new moon in a single calendar month.

A Black Moon (in some parts of the world)

The Black Moon is a somewhat unusual celestial event — they occur about once every 32 months, on average, and they sometimes only occur in certain time zones. The new moon occurring on Tuesday, Aug. 18 is a Black Moon. Officially, it occurs at 10:41 p.m. EDT (0241 GMT Aug. 19).  

The next Black Moon won't arrive until April 30, 2022, and it will be the second new moon in a single calendar month. The next Black Moon by the seasonal definition of the term will occur on May 19, 2023.

Seeing (or not seeing) a Black Moon

At its "new moon" phase, the moon is always black. It happens at that time of the month when the moon passes through the same part of the sky as the sun and as such, the moon's dark or unilluminated side faces Earth. So there really is nothing to see.

Actually, that's not always true, since there are times when the new moon passes directly between Earth and the sun and Earthlings can then see the moon's black silhouette crossing in front of the sun, causing a solar eclipse.

Wait for the crescent

If you have ever wondered where the term "new moon" originated, it simply refers to the start of a new lunar cycle. 

The time frame from one new moon to the next is called a synodic month, which, on average, lasts 29.53 days. This is the period of the moon's phases, because the moon's appearance depends on the position of the moon with respect to the sun as seen from the Earth. The word "synodic" is derived from the Greek word sunodikos, which means "meeting," for at new moon, the moon "meets" the sun.

But unlike a "supermoon," which gets countless numbers of people scurrying for vantage points to see a slightly larger and slightly brighter-than-average full moon, with a Black Moon, you simply can't see it.  

A couple of evenings later, however, you'll be able to pick out a slender sliver of a waxing crescent moon low in the western twilight sky about 30 or 40 minutes after sunset local time.

 Some people mistakenly refer to the appearance of any thin lunar crescent as the "new moon." This fallacy has even spread into popular literature. In his classic work "A Night to Remember," about the sinking of the Titanic, author Walter Lord quotes a fireman in a lifeboat who caught sight of a narrow crescent low in the dawn sky and exclaimed, "A new moon!"

A note on branding

As one who has been involved in the broadcasting field for nearly 40 years, I'd like to point out that we live in a time when the news media is seemingly obsessed with "branding." This marketing strategy involves creating a differentiated name and image — often using a tagline — in order to establish a presence in people's mind. In recent years in the field of astronomy, for example, we've seen annular eclipses — those cases when the moon is too small to completely cover the disk of the sun — become branded as "Ring of Fire" eclipses. A total eclipse of the moon — when the moon's plunge through the Earth's shadow causes the satellite to turn a coppery red color — is now referred to as a "Blood Moon." 

When a full moon is also passing through that part of its orbit that brings it closest to Earth — perigee — we now brand that circumstance as a supermoon. That term was actually conjured up by an astrologer back in 1979 but quite suddenly became a very popular media brand after an exceptionally close approach of a full moon to Earth in March 2011. It surprises me that even NASA now endorses the term, although it seems to me the astronomical community in general shies away from designating any perigee full moon as "super."

Then there is Blue Moon. This moniker came about because a writer for Sky & Telescope Magazine misinterpreted an arcane definition given by a now-defunct New England Almanac for when a full moon is branded "blue," and instead incorrectly reasoned that in a month with two full moons, the second is called a Blue Moon. That was a brand that quietly went unnoticed for some 40 years, until a syndicated radio show promoted the term in the 1980s and it then went viral. So now, even though the second full moon in a month is not the original definition for a Blue Moon, in popular culture we now automatically associate the second full moon in a calendar month with a Blue Moon.

So are you ready for yet another lunar brand? The newest one is Black Moon.

Editor's note: This article was originally published for the Black Moon of July 31, 2019 and updated for the Black Moon of Aug. 18, 2020.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmer's Almanac and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y. Follow us on Twitter @Spacedotcom and on Facebook.

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community@space.com.

Adam = Man or Humankind?

Adamah is a word, translatable as ground or earth, which occurs in the Biblical account of Creation of the Book of Genesis. The etymological link between the word adamah and the word adam is used to reinforce the teleological link between humankind and the ground, emphasising both the way in which man was created to cultivate the world, and how he originated from the "dust of the ground". Because man is both made from the adamah and inhabits it, his duty to realise his own potential is linked to a corresponding duty to the earth. In Eden, the adamah has primarily positive connotations, although Adam's close relationship with the adamah has been interpreted as likening him to the serpent, which crawls upon the ground, thus emphasising his animal nature.

Adam (Hebrew: אָדָם, Modern: ʼAdam, Tiberian: ʾĀḏām; Arabic: آدَم‎, romanized: ʾĀdam; Greek: Ἀδάμ, romanized: Adám; Latin: Adam) is a figure in the Book of Genesis in the Hebrew Bible, from where he was adopted into Christian belief and the Quran. According to the creation myth^[1] of the Abrahamic religions, he was the first man. In both Genesis and Quran, Adam and his wife were expelled from a Garden of Eden for eating the fruit of the tree of knowledge of good and evil.

Various forms of creationism and biblical literalism consider Adam to be a historical person. Scientific evidence does not support the idea that the entire human population descends from a single man.^{[2][3][4][5][6]}

The word adam is also used in the Bible as a pronoun, individually as "a human" and in a collective sense as "mankind".^[7] Biblical Adam (man, mankind) is created from adamah (earth), and Genesis 1–8 makes considerable play of the bond between them, for Adam is estranged from the earth through his disobedience.^[8] 

Origin

The majority view among scholars is that the book of Genesis dates from the Persian period (the 5th and 4th centuries BCE),^[9] but the absence from the rest of the Hebrew Bible of all the other characters and incidents mentioned in chapters 1–11 of Genesis, (Adam appears only in chapters 1–5, with the exception of a mention at the beginning of the Books of Chronicles where, as in Genesis, he heads the list of Israel's ancestors^[10]) has led a sizable minority to the conclusion that Genesis 1–11 was composed much later, possibly in the 3rd century BCE.^[11]

Usage

Mankind—human being—male individual

The Bible uses the word אָדָם ( 'adam ) in all of its senses: collectively ("mankind", Genesis 1:27), individually (a "man", Genesis 2:7), gender nonspecific ("man and woman", Genesis 5:1-2), and male (Genesis 2:23-24).^[7] In Genesis 1:27 "adam" is used in the collective sense, and the interplay between the individual "Adam" and the collective "humankind" is a main literary component to the events that occur in the Garden of Eden, the ambiguous meanings embedded throughout the moral, sexual, and spiritual terms of the narrative reflecting the complexity of the human condition.^[12] Genesis 2:7 is the first verse where "Adam" takes on the sense of an individual man (the first man), and the context of sex is absent; the gender distinction of "adam" is then reiterated in Genesis 5:1–2 by defining "male and female".^[7]

Connection to the earth

A recurring literary motif is the bond between Adam and the earth (adamah): God creates Adam by molding him out of clay in the final stages of the creation narrative. After the loss of innocence, God curses Adam and the earth as punishment for his disobedience. Adam and humanity are cursed to die and return to the earth (or ground) from which he was formed.^[13] This "earthly" aspect is a component of Adam's identity, and Adam's curse of estrangement from the earth seems to describe humankind's divided nature of being earthly yet separated from nature.^[13] God himself, who took of the dust from all four corners of the earth with each color (red, black, white, and green), then created Adam therewith,^[14] where the soul of Adam is the image of God.^[15]

In the Hebrew Bible

Genesis 1 tells of God's creation of the world and its creatures, with humankind as the last of his creatures: "Male and female created He them, and blessed them, and called their name Adam ..." (Genesis 5:2). God blesses mankind, commands them to "be fruitful and multiply", and gives them "dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth" (Genesis 1.26-27).

In Genesis 2, God forms "Adam", this time meaning a single male human, out of "the dust of the ground" and "breathed into his nostrils the breath of life" (Genesis 2:7). God then places this first man in the Garden of Eden, telling him that "Of every tree of the garden thou mayest freely eat: But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die" (Genesis 2:16-17). God notes that "It is not good that the man should be alone" (Genesis 2:18) and brings the animals to Adam, who gives them their names, but among all the animals there was not found a companion for him (Genesis 2:20). God causes a deep sleep to fall upon Adam and forms a woman (Genesis 2:21-22), and Adam awakes and greets her as his helpmate.

Genesis 3, the story of the Fall: A serpent persuades the woman to disobey God's command and eat of the tree of knowledge, which gives wisdom. Woman convinces Adam to do likewise, whereupon they become conscious of their nakedness, cover themselves, and hide from the sight of God. God questions Adam, who blames the woman. God passes judgment, first upon the serpent, condemned to go on his belly, then the woman, condemned to pain in childbirth and subordination to her husband, and finally Adam, who is condemned to labour on the earth for his food and to return to it on his death.^[16] God then expels the man and woman from the garden, lest they eat of the Tree of Life and become immortal.

The chiastic structure of the death oracle given to Adam in Genesis 3:19 forms a link between man's creation from "dust" (Genesis 2:7) to the "return" of his beginnings.^[17]

A you return

B to the ground

C since (kî ) from it you were taken

C' for (kî ) dust you are

B' and to dust

A' you will return

Genesis 4 deals with the birth of Adam's sons Cain and Abel and the story of the first murder, followed by the birth of a third son, Seth. Genesis 5, the Book of the Generations of Adam, lists the descendants of Adam from Seth to Noah with their ages at the birth of their first sons (except Adam himself, for whom his age at the birth of Seth, his third son, is given) and their ages at death (Adam lives 930 years). The chapter notes that Adam had other sons and daughters after Seth, but does not name them.

Post-Biblical Jewish traditions

Body

Adam possessed a body of light, identical to the light created by God on the first day.^[18] According to Jewish mystical tradition the original glory of Adam can be regained through mystical contemplation of God.^[8]

Adam, Lilith and Eve

The rabbis, puzzled by the verse of Genesis 1 which states that God created man and woman together, told that when God created Adam he also created a woman from the dust, as he had created Adam, and named her Lilith; but the two could not agree, for Adam wanted Lilith to lie under him, and Lilith insisted that Adam should lie under her, and so she fled from him, and Eve was created from Adam's rib.^[19] Her story was greatly developed, during the Middle Ages, in the tradition of Aggadic midrashim, the Zohar and Jewish mysticism. Other rabbis explained the same verse as meaning that Adam was created with two faces, male and female, or as a single hermaphrodite being, male and female joined back to back, but God saw that this made walking and conversing difficult, and so split them apart.^[20]

Eve's fault in the Fall

The serpent approached Eve rather than Adam because Adam had heard the word of God with his own ears, whereas Eve had only his report; Eve tasted the fruit and knew at once that she was doomed to death, and said to herself that it was better she trick Adam into eating so that he too would die, and not take another woman in her place.^[21] Adam ate the fruit unaware of what he was doing, and was filled with grief.^[21] When Adam blamed Eve after eating the forbidden fruit, God rebuked him that Adam as a man should not have obeyed his wife, for he is the head, not her.^[22]

Children of Adam and Eve

Adam withdrew from Eve for 130 years after their expulsion from Eden, and in this time both he and Eve had sex with demons, until at length they reunited and Eve gave birth to Seth.^[19] A 2nd-century BCE Jewish religious work, the Book of Jubilees, tells how Adam had a daughter, Awân, born after Cain and Abel,^[23] and another daughter, Azûrâ, born after Seth,^[24] and they had nine other sons;^[25] Cain married Awân and Seth married Azûrâ, thus accounting for their descendants. The Life of Adam and Eve and its Greek version the Apocalypse of Moses recount how Adam repented his sin in exile and was rewarded by being transported to the heavenly paradise, foreshadowing the destiny of all the righteous at the end of time.^[8]

Adam's death and burial

The Archangel Michael attended Adam's death, together with Eve and his son Seth, still living at that time, and he was buried together with his murdered son Abel.^[26] Because they repented, God gave Adam and Eve garments of light, and similar garments will clothe the Messiah when he comes.^[27]

According to the Apocalypse of Moses, which probably originates in first-century CE Jewish literature, the altar of the Temple of Solomon was the centre of the world and the gateway to God's Garden of Eden, and it was here that Adam was both created and buried.^[28]

Attitude towards Adam

In the 17th-century book Kav ha-Yashar, the author warns not to talk negatively about Adam, and writes that those who talk positively about Adam will be blessed with a long life.^[29] A similar warning can be found in The Zohar.^[30]

Adam and the angel Raziel

The Sefer Raziel HaMalakh (רזיאל המלאך) (Raziel the Angel) is a collection of esoteric writings, probably compiled and edited by the same hand, but originally not the work of one author, which according to tradition was revealed to Adam by the angel Raziel. The book cannot be shown to predate the 13th century, but may in parts date back to Late Antiquity, and like other obscure ancient texts such as the Bahir and Sefer Yetzirah, it has been extant in a number of versions. Zunz ("G. V." 2d ed., p. 176) distinguishes three main parts: (1) the Book Ha-Malbush; (2) the Great Raziel; (3) the Book of Secrets, or the Book of Noah. These three parts are still distinguishable—2b–7a, 7b–33b, 34a and b. After these follow two shorter parts entitled "Creation" and "Shi'ur Ḳomah", and after 41a come formulas for amulets and incantations.^[31]

In Christianity

For the Christian doctrines, see Fall of man and Original sin.

Original sin

The idea of original sin is not found in Judaism nor in Islam, and was introduced into Christianity by the Apostle Paul, drawing on currents in Hellenistic Jewish thought which held that Adam's sin had introduced death and sin into the world.^[32][33] Sin, for Paul, was a power to which all humans are subject, but Christ's coming held out the means by which the righteous would be restored to the Paradise from which Adam's sin had banished mankind.^[33][8] He did not conceive of this original sin of Adam as being biologically transmitted or that later generations were to be punished for the deeds of a remote ancestor.^[33] It was Augustine who took this step, locating sin itself in male semen: when Adam and Eve ate of the fruit they were ashamed and covered their genitals, identifying the place from which the first sin was passed on to all succeeding generations.^[34] Only Jesus Christ, who was not conceived by human semen, was free of the stain passed down from Adam.^[35] (Augustine's idea was based on the ancient world's ideas on biology, according to which male sperm contained the entire unborn baby, the mother's womb being no more than a nurturing chamber in which it grew.)^[36]

Adam's grave: Golgotha replaces Solomon's Temple

As mentioned above, the Apocalypse of Moses, a Jewish writing containing material probably originating from the first century CE, places both Adam's place of creation and his burial at the altar of the Temple of Solomon, seen as the centre of the world and the gateway to the Garden of Eden.^[28] The early Christian community adapted this to their own legend of Golgotha, replacing the altar with the place of Jesus's crucifixion.^[37] According to this Christian legend, current in the time of Origen (early 3rd century CE), the holy blood of Christ trickled down and restored to life the father of the human race, who then led the saints who appeared to many in Jerusalem on that day as described in Scripture.^[38]

In Islam

In Islam, God created Adam (Arabic: آدم) from a handful of earth taken from the entire world, which explains why the peoples of the world are of different colours.^[39] According to the Islamic creation myth, he was the first prophet of Islam and the first Muslim. The Quran says that all the prophets preached the same faith of submission to God. When God informed the angels that he would create a vice-regent (a khalifa) on Earth, the angels enquired, saying, "will You place therein such that will spread corruption and bloodshed?" So God showed the angels, saying, "Tell Me the names of these?" The angels had no knowledge of these, as God had not taught them. Then God allowed Adam to reveal these names to them, saying, "Did I not say to you (angels) that I know what is unseen in the heavens and the earth and I know what you (angels) reveal and what you (Satan) conceal;" the scholar Al-Tabari explained that God was referring to Iblis (Satan) of his evil plans and to the angels of their honesty.^[40]

Adam and Eve both ate of the Tree of Immortality, and both shared guilt equally, for Eve neither tempted Adam or ate before him; nor is Eve to blame for the pain of childbirth, for God never punishes one person for the sins of another.^[41] The Shia school of Islam does not even consider that their action was a sin, for obedience and disobedience are possible only on Earth and not in heaven, which is the location of Paradise.^[41] Adam fell on a mountain in India, the tallest in the world and so the closest to Heaven, and from there God sent him to Mecca, where he repented and was forgiven.^[42] At Mecca he built the first Sanctuary (the Kaabah - it was later rebuilt by Ibrahim) and was taught the ritual of the Hajj, and wove the first cloak for himself and the first veil and shift for Eve, and after this returned to India where he died at the age of 930, having seen the sons of the sons of his children, 1400 in all.^[43]

According to the Ahmadiyya sect Adam was not the first human being on earth, but when the human race came into existence, and spread all over the world and developed the ability to receive revelation, God sent Adam to each and every branch and civilization. According to a revelation received by Mirza Ghulam Ahmad, the founder of the community, the Adam mentioned in the Quran was born 4,598 years before Muhammad.^[44]

In the Quran Adam is given the name by God known as the (Adam-I-Safi) or The Chosen One.^[45][46]

Nicene Christianity

Nicene Christianity is a set of Christian doctrinal traditions which reflect the Nicene Creed, which was formulated^[1] at the First Council of Nicaea in AD 325 and amended at the First Council of Constantinople in AD 381.^[2]

History

At the time of the First Council of Nicaea, the main rival of Nicene Christian doctrine was that of Arianism, which became eclipsed during the 7th century AD with the conversion of the Gothic kingdoms to Nicene Christianity. The main points of dissent between the two centered on Christology, or the nature of Jesus' divinity. Nicene Christianity regards Jesus as divine and co-eternal with God the Father, while Arianism treats him as the first among created beings and inferior to God the Father. Various other non-Nicene doctrines and beliefs have existed since the early medieval period, all of which have been considered heresies.^[1]

Today's mainstream Christian Churches (including all of the Catholic, Eastern Orthodox, Oriental Orthodox, Assyrian and Ancient Churches, Lutheran and Anglican churches, as well as most Protestant denominations) adhere to the Nicene Creed and thus exemplify Nicene Christianity.

Major denominational families in Christianity:

This box: 

• view
• talk
• edit

Western Christianity

Eastern Christianity

Protestantism

Evangelicalism

Anabaptism

Anglicanism

Calvinism

Lutheranism

(Latin Church)

Catholic Church

(Eastern Catholic Churches)

Eastern Orthodox Church

Oriental Orthodox Churches

Church of the East

Nestorianism

Schism (1552)

Assyrian Church of the East

Ancient Church of the East

Protestant Reformation

(16th century)

Great Schism

(11th century)

Council of Ephesus (431)

Council of Chalcedon (451)

Early Christianity

State church of the
Roman Empire

"Great Church"

(Full communion)

(Not shown are non-Nicene, nontrinitarian, and some restorationist denominations.)

Chalcedonian Christianity forms a large subset of Nicene Christianity. In addition to subscribing to the Nicene Creed, Chalcedonian Christians also subscribe to the decisions of the First Council of Ephesus in AD 431 and of the Council of Chalcedon in AD 451. Most Nicene Christians also adhere to the beliefs of Chalcedonian Christians, as defined by the Chalcedonian Creed. However, those denominations that hold to the Nicene Creed, but do not adhere to the Chalcedonian Definition (or the Chalcedonian Creed), include portions of Eastern Christianity (i.e., the Oriental Orthodox Churches and, historically, the Church of the East [which also rejects the outcome of the First Council of Ephesus]) and would therefore be considered non-Chalcedonian Nicene Christians.

Today, examples of non-Nicene Christian denominations encompass both Protestant and non-Protestant non-trinitarian groups. Examples of these groups include the majority of the Latter Day Saint movement (with the exception of the Nicene Mormon group known as the Community of Christ [formerly known as the Reorganized Church of Jesus Christ of Latter Day Saints]), the Unitarian Church of Transylvania, Oneness Pentecostals, and others.

See also[edit]

• Church Fathers
• First seven Ecumenical Councils
• State church of the Roman Empire

First Humans may have arrived on the American continent 30,000 years ago

First Americans may have arrived to the continent 30,000 years ago

By Laura Geggel - Associate Editor

However, they didn't have a population boom until about 14,700 years ago.

The early inhabitants of North America left behind precious few clues of their existence — a footprint here, a weapon and a mummy there — leading scientists to wonder exactly when the first people arrived on the continent. 

Now, two new studies report a stunningly early date: Humans may have been living on the continent at least 30,000 years ago. 

That would mean that the first North Americans may have arrived before the Last Glacial Maximum (LGM), between about 26,500 and 19,000 years ago, when ice sheets covered much of what is now the northern U.S. and Canada. However, humans didn't become widespread on the continent until about 14,700 years ago, when the population boomed. 

"These are fascinating studies," said William Harcourt-Smith, a paleoanthropologist at Lehman College and the American Museum of Natural History, both based in New York City, who wasn't involved with the research. "It's now very clear that modern humans were in the Americas far earlier than we used to think. There have been other sites and scholars suggesting this, but it is rigorous studies like this that really seals the deal."

In one study, archaeologists analyzed a remote cave in northwestern Mexico containing human-made stone tools that are up to 31,500 years old, according to dating models. This would push back dates for human dispersal into North America to as early as 33,000 years ago, the researchers said. 

In the other study, archaeologists took already-published dates from 42 archaeological sites in North America and Beringia (the region that historically connected Russia and America), and plugged them into a model that analyzed human dispersal. This model found an early human presence in North American dating to at least 26,000 years ago. 

Both studies, published online today (July 22) in the journal Nature, go against the "Clovis-first" model, a decades-old hypothesis that early humans arrived in the Americas via Beringia as the last ice age was ending, about 13,000 years ago. However, scientists have been chipping away at this model for years, as even older sites, including the newly analyzed cave in Mexico, are discovered and dated.

 

Cave in the mountains
In 2010, researchers found ancient stone tools in Chiquihuite Cave, a site in the mountains that sits 9,000 feet (2,740 meters) above sea level and about 3,200 feet (1,000 m) above the valley floor, the researchers wrote in the study. The terrain at the cave is challenging to navigate — the roof at the cave's entrance collapsed about 12,000 years ago, sealing it off — so the team did excavations about 165 feet (50 m) inside the cave. It was so hard to travel to and from the cave, that the archaeologists ended up living at the site for two seasons — a total of 80 days — in 2016 and 2017.

During that time, the team worked steadily, collecting bone, charcoal and sediment. They used two techniques to date the roughly 1,900 stone tools in the cave:  radiocarbon dating and optically stimulated luminescence (OSL). With OSL, researchers assessed when quartz grains in the sediment had last been exposed to sunlight. To avoid biasing the results, "when we extracted the samples, it had to be in complete darkness," said study lead researcher and director of the excavation, Ciprian Ardelean, an archaeologist at the Autonomous University of Zacatecas.

 The radiocarbon dating and the OSL dates matched, suggesting that the dating was accurate, Ardelean said. Then, the researchers divided the layers into two main sections — a younger layer dating to between 16,600 and 12,200 years ago, which contained about 88% of the stone tools, and an older layer that was about 16,600 to 33,000 years old, which held about 12% of the stone tools.

Ardelean noted that the stone tools show clear signs of human sculpting, including signs that ancient humans hit one type of rock with another to make a sharp, pointed edge, known as a flake.  "You can also see repeated blows on the same spot from different angles when it was harder for them to separate the flakes and they are trying again and again," Ardelean told Live Science. 

However, a hunt for genetic material in the cave yielded only plant and animal DNA (including junipers, firs and pines, bats, bears, voles, deer mice and marmots), but not human DNA. 

The tools were of a style never seen before by archaeologists, but this style didn't change much over the thousands of years. Also, there weren't many tools given how long the cave was used, so it appears that the cave was used sparsely, he said. More evidence of human activity may lie closer to the entrance of the cave, but that area would be challenging to excavate because of the collapsed entrance, he said. 

In addition, the team found evidence of sulfur, potassium and zinc, elements that could be signs of human activities, such as butchering animals or urination, although it's also possible that these elements were left by carnivores using the cave, Ardelean said.

Chiquihuite Cave is one of the few analyzed sites indicating that humans lived in North America before the beginning of the LGM, said Justin Tackney, an associate researcher in the Department of Anthropology at the  University of Kansas, who was not involved in the study.

"If the authors are correct, Chiquihuite Cave would represent a very significant discovery in our field," because the site was used up to about 30,000 years ago, Tackney told Live Science. "This would then lead to questions of which physical routes would these humans have taken to get that far south at such an early date, particularly during the maximal extent of the ice sheets."

These dates are so early, "the focus now will be on the veracity of those few older lithic artifacts," Tackney said.

However, the analysis of all of these stone tools shows that the humans who used the cave were flexible enough to deal with the elements so high above sea level, Harcourt-Smith said. What's more, "it shows that Mexico is an important region to be focusing on in relation to understanding the earliest humans in the Americas," Harcourt-Smith told Live Science.

North American travels

The other study pulled data from archaeological analyses of early North American sites. In particular, the researchers were interested when humans first began occupying each site, "since people are present in a region before an archaeological site is created," said study lead researcher Lorena Becerra Valdivia, an archaeological scientist at the University of Oxford in England and the University of New South Wales in Australia. 

"It is reasonable to assume, for example, that there were people in North America before we see their trace in Mexico at Chiquihuite Cave," Becerra Valdivia told Live Science in an email. "In this way, our study was to identify large-scale patterns of human migration into and through the continent over time."

After analyzing data from 42 archaeological sites across the continent, the researchers found that "whilst there were humans in North America before, during and immediately after the Last Glacial Maximum, populations expanded significantly across the continent much later, during a period of abrupt global climate warming at the end of the Ice Age, beginning at around 14,700 years ago," said Becerra Valdivia, who was also a co-researcher on the Chiquihuite Cave study. 


This analysis is based on the fact that three major stone tool traditions — the Clovis, Western Stemmed and Beringian — all began at about the same time, as well as genetic evidence that points to a population spike. This population growth likely played a role in the decline of large animals such as mammoths and camels, although climate change at the end of the last ice age likely contributed too, she said. 

"It seems, therefore, that the initial arrivals did not have a marked, immediate impact in megafaunal decline," Becerra Valdivia said. "Population expansion and growth later on were key."

Related: 10 Extinct Giants That Once Roamed North America

She acknowledged that because this study focuses only on North American, similar research on South America is needed. "Only by unlocking the history of initial human occupation there [in South America] will we be able to see the entire picture and understand the full migration pattern," Becerra Valdivia said.

This statistical modeling does make some assumptions about occupation dates, "making their conclusions more open to interpretation and debate," Harcourt-Smith said. However, it also shows "that if we take a total evidence approach to the first occupation of the Americas, the data suggest (only suggest) that humans may have been around as far back as 30,000 years ago, which is extraordinary," Harcourt-Smith said. "Obviously, we'll need hard evidence [such as human remains or DNA] to back up this suggestion, but it's exciting to think about."


Originally published on Live Science.