In the Jurassic era early mammals lived much longer, but matured much later, impairing their ability to overcome threats to their respective species by reproducing early and often. Evolutionary fitness favored the modern pattern.
Researchers were able to image tiny growth rings in fossilized root cement -- the bone tissue that attaches the teeth to the jaw. "The rings are similar to those in trees, but on a microscopic level," explains Professor Thomas Martin of the Vertebrates -- Mammals working group at the University of Bonn Institute of Organismic Biology, who is a senior author of the study. "Counting the rings and analyzing their thickness and texture enabled us to reconstruct the growth patterns and lifespans of these extinct animals."The researchers determined that the first signs of the growth patterns characteristic of modern mammals, such as a puberty growth spurt, started emerging roughly 150 million years ago. Early mammals grew much more slowly but lived substantially longer than today's small mammals, with lifespans of eight to fourteen years instead of just one or two as in modern mice, for example. However, it took early mammals years to reach sexual maturity, again in contrast to their modern descendants which reach sexual maturity in just a few months.
From Science Daily citing Elis Newham, et al., "The origins of mammal growth patterns during the Jurassic mammalian radiation." 10(32) Science Advances (2024) DOI: 10.1126/sciadv.ado4555
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ReplyDeletehttps://www.sciencedirect.com/science/article/abs/pii/S0047248423000908
Morphological and morphometric analyses of a late Middle Pleistocene hominin mandible from Hualongdong, China
Author links open overlay panelXiujie Wu a, Shuwen Pei a, Yanjun Cai b, Haowen Tong a, Ziliang Zhang c, Yi Yan a d, Song Xing a, María Martinón-Torres e
, José María Bermúdez de Castro e, Wu Liu aShow more
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https://doi.org/10.1016/j.jhevol.2023.103411
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Abstract
Excavations in Hualongdong (HLD), East China, have yielded abundant hominin fossils dated to 300 ka. There is a nearly complete mandible that fits well with a partial cranium, and together they compose the skull labeled as HLD 6. Thus far, detailed morphological description and comparisons of the mandible have not been conducted. Here we present a comprehensive morphological, metric, and geometric morphometric assessment of this mandible and compare it with both adult and immature specimens of Pleistocene hominins and recent modern humans. Results indicate that the HLD 6 mandible exhibits a mosaic morphological pattern characterized by a robust corpus and relatively gracile symphysis and ramus. The moderately developed mental trigone and a clear anterior mandibular incurvation of the HLD 6 mandible are reminiscent of Late Pleistocene hominin and recent modern human morphology. However, the weak expression of all these features indicates that this mandible does not possess a true chin. Moreover, a suite of archaic features that resemble those of Middle Pleistocene hominins includes pronounced alveolar planum, superior transverse torus, thick corpus, a pronounced endocondyloid crest, and a well-developed medial pterygoid tubercle. The geometric morphometric analysis further confirms the mosaic pattern of the HLD 6 mandible. The combination of both archaic and modern human features identified in the HLD 6 mandible is unexpected, given its late Middle Pleistocene age and differs from approximately contemporaneous Homo members such as Xujiayao, Penghu, and Xiahe. This mosaic pattern has never been recorded in late Middle Pleistocene hominin fossil assemblages in East Asia. The HLD 6 mandible provides further support for the high morphological diversity during late Middle Pleistocene hominin evolution. With these findings, it is possible that modern human morphologies are present as early as 300 ka and earlier than the emergence of modern humans in East Asia.
https://www.cnn.com/2023/08/10/asia/ancient-skull-china-human-evolution-intl-scli-scn/index.html
300,000-year-old skull found in China unlike any early human seen before
https://www.youtube.com/watch?v=2vyHhFCE0mo&t=1085s
What on Earth is HLD 6?
here's the question,
according to recent out of Africa
anatomically modern humans left Africa around 60k years and started to colonize Asia then Europe
but this fossil skull is uranium dated 300k years ago but has mosiac erectus and sapien and neanderthal like features
https://en.wikipedia.org/wiki/Hualongdong_people
In 2020, a well preserved lower jawbone (mandible) was discovered among animal fossils that was found to be part of HLD 6.[7] The analysis, reported in 2023, revealed that the individual shows a clear mixture of different archaic and modern humans.[18] A thick bone along the jawline is a common feature with H. erectus. A notable archaic appearance is the lack of true chin.[7] A true chin a defining feature of modern humans and is absent in archaic species. HLD 6 jawline is more similar to those of Denisovans than to any other humans.[5]
the original evidence for multiregionalism are these Chinese fossils with mosaic erectus and sapien like features, erectus-sapien like homins with sapien like 1300cc brains, now DNA has shown multiregionalism to be wrong explanation for modern humans are recent out of Africa, but that still begs the question, what is going on in China with these erectus-sapien mosiacs, 300k years ago Middle Pleistocene. maybe Deniosovan-erectus hybrids.
Thanks for the heads up. I was aware of the paper but I could only really do it justice in a much longer post over several recent papers on the topic, which I haven't had the time to do.
ReplyDeletethis video discuss the paper
ReplyDeleteWhat on Earth is HLD 6?
https://www.youtube.com/watch?v=2vyHhFCE0mo&t=1085s
discuss 300kya Chinese archaic
she's said Chris Stinger and of course Chinese academics are trying to figure out Chinese archaic
Homo sapiens in the Eastern Asian Late Pleistocene
The University of Chicago Press: Journals
https://www.journals.uchicago.edu › doi › full
by M Martinón-Torres · 2017 · Cited by 67 — 2017; Martinón-Torres et al. 2016; Xing et al. 2016). New fossil and genetic data suggest that along with “classic” Homo erectus, Asia has
what do you think ?
perhaps a very early sapiens out of Africa 350kya enter China and mix with erectus
Modern humans didn't even exist prior to 300 kya, so not that. The earliest evidence of Out of Africa is about 150-125 kya. The most plausible hypothesis, from all of the evidence, is that modern humans made it only as far as India prior to the Toba eruption and that this is a causal relationship - i.e. that the eruption cleared the way for modern humans to traverse SE Asia somehow. Denisovan-Homo Erectus admixture, or local convergent evolution could explain these old mosaic remains.
ReplyDeletehave you seen there is this
ReplyDelete2020 Dec 19;157(1):51.
doi: 10.1186/s41065-020-00163-9.
The reversal of human phylogeny: Homo left Africa as erectus, came back as sapiens sapiens
Úlfur Árnason 1 , Björn Hallström 2
Abstract
Background: The molecular out of Africa hypothesis, OOAH, has been considered as an established fact amid population geneticists for some 25-30 years despite the early concern with it among phylogeneticists with experience beyond that of Homo. The palaeontological support for the hypothesis is also questionable, a circumstance that in the light of expanding Eurasian palaeontological knowledge has become accentuated through the last decades.
Results: The direction of evolution in the phylogenetic tree of modern humans (Homo sapiens sapiens, Hss) was established inter alia by applying progressive phylogenetic analysis to an mtDNA sampling that included a Eurasian, Lund, and the African Mbuti, San and Yoruba. The examination identified the African populations as paraphyletic, thereby compromising the OOAH. The finding, which was consistent with the out of Eurasia hypothesis, OOEH, was corroborated by the mtDNA introgression from Hss into Hsnn (Neanderthals) that demonstrated the temporal and physical Eurasian coexistence of the two lineages. The results are consistent with the palaeontologically established presence of H. erectus in Eurasia, a Eurasian divergence between H. sapiens and H. antecessor ≈ 850,000 YBP, an Hs divergence between Hss and Hsn (Neanderthals + Denisovans) ≈ 800,000 YBP, an mtDNA introgression from Hss into Hsnn* ≈ 500,000 YBP and an Eurasian divergence among the ancestors of extant Hss ≈ 250,000 YBP at the exodus of Mbuti/San into Africa.
Conclusions: The present study showed that Eurasia was not the receiver but the donor in Hss evolution. The findings that Homo left Africa as erectus and returned as sapiens sapiens constitute a change in the understanding of Hs evolution to one that conforms to the extensive Eurasian record of Hs palaeontology and archaeology.
Hum... the problem with that Arnason paper is that the mtDNA diversity in Africa is higher that Europe. To get the hss components into all the divergent African linages would more admixture edges than the converse, and is therefore less likely.
ReplyDeletehe also note that that Hs mixed with African archaic so mtDNA diversity in Africa is higher that Europe
ReplyDeleteBack on topic, late maturation seems a hallmark of marsupials. They can mature late because they live in a pouch. Placentals by contrast mature early because they leave the mother entirely at birth; there's no halfway stage, the mother must nurse the infant and keep watch.
ReplyDeleteThumbs down to Árnason. It can pretty much be dismissed out of hand. The evidence against it from multiple disciplines is overwhelming.
ReplyDelete@Darayvus Interesting observation.
ReplyDelete