Plant Life Through the Ages
Panel 1: Age of Stromatolites
Late Archaean Eon — 3,500-1,250 million years ago
Panel 2: Rhynie Chert Flora
Early Devonian Period — About 400 million years ago
Panel 3: Rise of a Land Flora
Early and Middle Devonian Period — 416–385 million years ago
Panel 4: First Forests
Late Devonian Period — 385-360 million years ago
Panel 5: Carboniferous Coal Swamp Forests
Late Carboniferous Period — 323-300 million years ago
Panel 6: Age of Gymnosperms
Triassic Period through early Early Cretaceous Period — 250–130 million years ago
Panel 7: Rise of the Flowering Plants
Late Early Cretaceous Period through Cretaceous Period —130–65 million years ago
Panel 8: Plants and Human Affairs
The Holocene Epoch — The last 11,500 years
Culture Clovis
Quelles sont les plus vieilles traces d’occupation humaine retrouvées au Québec?
Les plus vieilles traces d’activités humaines trouvées à ce jour dans la province s’apparentent à la culture Clovis et ont environ 12 000 ans.
Il est à noter que les restes humains datant de cette époque sont rarissimes. On tente donc de comprendre l’histoire des premiers occupants de l’Amérique indirectement à partir d’artéfacts. La culture Clovis correspond à une méthode de travail reconnaissable, une technique de taille de la pierre bien particulière partagée par certaines populations humaines il y a entre 13,000 et 12,600 ans. C’est une très brève période à l’échelle de notre histoire, un «snapshot» dans le temps avant que cette culture évolue et que les techniques pour travailler la pierre changent.
Est-ce que cela signifie que les premiers humains en Amérique/Québec appartenaient à la culture Clovis?
Pas nécessairement.
Toute la dernière moitié du 20e siècle, lorsque des signes d’occupation humaine prédatant la culture Clovis étaient découverts, ils étaient systématiquement discrédités. Il en allait de même pour les voix autochtones argumentant que leur présence en Amérique était plus ancienne que la culture Clovis, un comportement qualifié par certains de «violence académique».
Éventuellement, assez d’indices se sont accumulés pour ébranler le consensus voulant que le peuple Clovis ait été la première présence humaine en Amérique via le passage par le détroit de Béring. Notre compréhension des évènements demeure limitée, mais on soupçonne que des individus seraient parvenus en Amérique en longeant la côte ouest à bord d’embarcations primitives avant que le détroit de Béring ne permette le passage à pied. Malheureusement, la montée des eaux a probablement englouti bien des traces de cette exploration côtière.
Est-ce que les nations autochtones modernes sont des descendants du peuple Clovis?
Selon les analyses génétiques effectuées à partir de l’unique dépouille trouvée d’un individu associé à la culture Clovis (un bambin enterré avec des artéfacts Clovis au Montana, surnommé Anzick), de nombreuses nations autochtones modernes sont des descendants directs de la métapopulation à laquelle Anzick appartenait. Cette affirmation s’applique surtout aux nations du sud, tandis que les nations au nord partagent plutôt des ancêtres communs avec la population Clovis d’Anzick, sans en être des descendants directs. En d’autres mots, un groupe initial englobant potentiellement plusieurs cultures, dont la culture Clovis, s’est divisé en deux branches distinctes : nord et sud.
Dans la figure suivante, deux hypothèses concordantes avec les analyses génétiques illustrent comment les populations nord-américaines (NA) auraient divergé des sud-américaines (SA).
Un autre facteur à prendre en considération est le fait que plusieurs événements de migration vers les Amériques ont eu lieu, autant avant qu’après la propagation de la culture Clovis à travers le continent. Ces populations auraient pu se croiser, se mélanger, se diviser, se remélanger, etc. Bref, il s’agit d’un sujet complexe qui n’a pas fini de nous révéler tous ses mystères!
Geneviève Coudé, MSc en écologie
Aucune mention de Jésus dans 126 textes contemporains
Jesus never existed. That is the conclusion of a researcher who says he has combed 126 texts written during or shortly after the time Jesus is supposed to have lived — and found no mention of Jesus whatsoever.
(...) In a new article entitled “The Fable of the Christ,” Michael Paulkovich summarizes his findings, or lack of findings, which lead him to believe that Jesus never actually existed, but is instead a fictional character, made up to give followers of the religion founded in his name a central icon worthy of their worship.
Paulkovich says that only one of the 126 texts he combed through contains any mention of Jesus — and that, he says, is a forgery. That text is the first-century history book The Jewish Wars by the Roman historian Josephus Flavius, who wrote his work in the year 95 CE.
But, despite making his home just one mile from Jesus’s supposed hometown of Nazareth, Josephus appears totally unaware of the famous miracle worker who later went to Jerusalem where he became such a political threat that the Romans found it necessary to execute him by crucifixion.
The few mentions of Jesus in The Jewish Wars, Paulkovich argues, were added by later editors, not by Josephus himself.
Otherwise, says the author, despite the remarkable feats Jesus is alleged to have performed and the great deal of political unrest caused by his arrival in Jerusalem, not a single writer from the time and place of Jesus’s life finds that Jesus so much as rates a footnote.
“Emperor Titus, Cassius Dio, Maximus, Moeragenes, Lucian, Soterichus Oasites, Euphrates, Marcus Aurelius, or Damis of Hierapolis. It seems none of these writers from first to third century ever heard of Jesus, global miracles and alleged worldwide fame be damned,” Paulkovich said in a recent interview.
The Dead Sea Scrolls, also known as the Qumran texts, also contain no mention of Jesus. Even the Apostle Paul, the New Testament figure credited with spreading the new religion that came to be called “Christianity” shortly after the supposed death of Jesus, never says that Jesus was a a real person — even in the Bible itself.
“Paul is unaware of the virgin mother, and ignorant of Jesus’ nativity, parentage, life events, ministry, miracles, apostles, betrayal, trial and harrowing passion,” Paulkovich states. “Paul knows neither where nor when Jesus lived, and considers the crucifixion metaphorical.”
(...) The invention of a mythical figure for followers of the cult to rally around gave the early Christians the strength to survive, according to this theory. On the other hand, another recent advocate of the “Mythical Jesus” believes that Christ was invented by the Romans as propaganda to pacify the public.
“When I consider those 126 writers, all of whom should have heard of Jesus but did not — and Paul and Marcion and Athenagoras and Matthew with a tetralogy of opposing Christs, the silence from Qumran and Nazareth and Bethlehem, conflicting Bible stories, and so many other mysteries and omissions,” Paulkovich writes, “I must conclude that Christ is a mythical character.”
Human ancestors nearly went extinct 900,000 years ago
Extrait de l'article:
Human ancestors in Africa were pushed to the brink of extinction around 900,000 years ago, a study shows. The work1, published in Science, suggests a drastic reduction in the population of our ancestors well before our species, Homo sapiens, emerged. The population of breeding individuals was reduced to just 1,280 and didn’t expand again for another 117,000 years.
“About 98.7% of human ancestors were lost,” says Haipeng Li, a population geneticist at the University of Chinese Academy of Sciences in Beijing, who co-led the study. He says that the fossil record in Africa and Eurasia between 950,000 and 650,000 years ago is patchy and that “the discovery of this bottleneck may explain the chronological gap”.
Nick Ashton, an archaeologist at the British Museum in London, who wrote a related perspective2, says he was intrigued by the tiny size of the population. “This would imply that it occupied a very localized area with good social cohesion for it to survive,” he says. “Of greater surprise is the estimated length of time that this small group survived. If this is correct, then one imagines that it would require a stable environment with sufficient resources and few stresses to the system.”
Clues from modern DNA
To make their discovery, the researchers needed to invent new tools. Advances in genome sequencing have improved scientists’ understanding of population sizes for the period after modern humans emerged, but the researchers developed a methodology that enabled them to fill in details about earlier human ancestors. Serena Tucci, an anthropologist at Yale University in New Haven, Connecticut, says that such work was sorely needed. “We still know very little about the population dynamics of early human ancestors for several reasons, including methodological limitations and difficulties in obtaining ancient DNA data from old Homo specimens,” she says.
The researchers’ method allowed them to reconstruct ancient population dynamics on the basis of genetic data from present-day humans. By constructing a complex family tree of genes, the team was able to examine the finer branches of the tree with greater precision, identifying significant evolutionary events.
The technique “put the spotlight on the period 800,000 to one million years ago — for which there is much unknown — in a way that hasn’t been done before,” says Stanley Ambrose, an anthropologist at the University of Illinois at Urbana-Champaign.
This period was part of the Early-Middle Pleistocene transition — a time of drastic climate change, when glacial cycles became longer and more intense. In Africa, this led to long periods of drought. Li says that the changing climate might have wiped out human ancestors and forced new human species to emerge. Eventually, these might have evolved into the last common ancestor of modern humans and our extinct relatives, the Denisovans and Neanderthals.
Around 813,000 years ago, the population of pre-humans began to swell again. How our ancestors managed to survive, and what allowed them to flourish once more, remains unclear, says Ziqian Hao, a population geneticist at the Shandong First Medical University and Shandong Academy of Medical Sciences in Jinan, and a co-author of the paper. However, he says that the bottleneck is likely to have had a crucial impact on human genetic diversity, driving many important features of modern humans, such as brain size. He estimates that up to two-thirds of genetic diversity was lost. “It represents a key period of time during the evolution of humans. So there are many important questions to be answered,” he says.
Ashton would like to see the researchers’ findings backed by more archaeological and fossil evidence. The authors “suggest that the bottleneck was a global crash in population”, he says, “but the number of archaeological sites outside Africa suggests that this is not the case. A regional bottleneck might be more likely.”
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