Humans have an unusual life history, with an early weaning age, long childhood, late first reproduction, short interbirth intervals, and long lifespan. In contrast, great apes wean later, reproduce earlier, and have longer intervals between births. Despite 80 y of speculation, the origins of these developmental patterns in Homo sapiens remain unknown. Because they record daily growth during formation, teeth provide important insights, revealing that australopithecines and early Homo had more rapid ontogenies than recent humans. Dental development in later Homo species has been intensely debated, most notably the issue of whether Neanderthals and H. sapiens differ. Here we apply synchrotron virtual histology to a geographically and temporally diverse sample of Middle Paleolithic juveniles, including Neanderthals, to assess tooth formation and calculate age at death from dental microstructure. We find that most Neanderthal tooth crowns grew more rapidly than modern human teeth, resulting in significantly faster dental maturation. In contrast, Middle Paleolithic H. sapiens juveniles show greater similarity to recent humans. These findings are consistent with recent cranial and molecular evidence for subtle developmental differences between Neanderthals and H. sapiens. When compared with earlier hominin taxa, both Neanderthals and H. sapiens have extended the duration of dental development. This period of dental immaturity is particularly prolonged in modern humans.
Posts: 6572 | From: N.Y.C....Capital of the World | Registered: Jun 2008
| IP: Logged |
posted
Modern Humans Mature More Slowly Than Neanderthals Did, Analysis of Teeth Suggests
(Nov. 15, 2010) — A sophisticated new examination of teeth from 11 Neanderthal and early human fossils shows that modern humans are slower than our ancestors to reach full maturity. The finding suggests that our characteristically slow development and long childhood are recent and unique to our own species, and may have given early humans an evolutionary advantage over Neanderthals.
The research, led by scientists at Harvard University, the Max Planck Institute for Evolutionary Biology (MPI-EVA), and the European Synchrotron Radiation Facility (ESRF), is detailed in the Proceedings of the National Academy of Sciences.
"Teeth are remarkable time recorders, capturing each day of growth much like rings in trees reveal yearly progress," says Tanya M. Smith, assistant professor of human evolutionary biology at Harvard. "Even more impressive is the fact that our first molars contain a tiny 'birth certificate,' and finding this birth line allows scientists to calculate exactly how old a juvenile was when it died."
Compared to even early humans, other primates have shorter gestation, faster childhood maturation, younger age at first reproduction, and a shorter overall lifespan. It's been unclear exactly when, in the 6 to 7 million years since our evolutionary split from non-human primates, the life course shifted.
Smith and her colleagues found that young Neanderthals' teeth growth -- a proxy for overall development -- was significantly faster than in our own species, including some of the earliest groups of modern humans to leave Africa some 90,000 to 100,000 years ago. This indicates that the elongation of childhood has been a relatively recent development.
Such studies add to the growing body of evidence that subtle developmental differences exist between us and our Neanderthal cousins. The recent sequencing of the Neanderthal genome has provided tantalizing genetic clues pointing to differences in cranial and skeletal development between Neanderthals and modern humans.
The current study involves some of the most famous Neanderthal children ever discovered, including the first hominin fossil, discovered in Belgium in the winter of 1829-30. This individual was previously thought, based on comparisons with modern humans, to have been four to five years old at the time of death. Now, powerful synchrotron X-rays and biological rhythms inside teeth have revealed the child was only three years old. While counting lines in teeth isn't a new method, Smith says, doing it "virtually" using synchrotron micro-computed tomography is.
"These new methods present a unique opportunity to assess the origins of a fundamentally human condition: the costly yet advantageous shift from a primitive 'live fast and die young' strategy to the 'live slow and grow old' strategy that has helped to make humans one of the most successful organisms on the planet," Smith says. Humans' extended maturation may have facilitated additional learning and complex cognition, possibly giving early Homo sapiens an advantage over their Neanderthal cousins.
Smith's co-authors are Paul Tafforeau of ESRF; Donald J. Reid of Newcastle University; Joane Pouech of MPI-EVA and ESRF; Vincent Lazzari of MPI-EVA, ESRF, and the International Institute of Paleoprimatology and Human Paleontology; John P. Zermeno of Harvard; Debbie Guatelli-Steinberg of Ohio State University; Anthony J. Olejniczak of MPI-EVA and the Centro Nacional de Investigación sobre la Evolución Humana; Almut Hoffman of the Museum für Vor- und Frühgeschichte; Jakov Radovčić of the Croatian Natural History Museum; Masrour Makaremi of University Bordeaux II; Michel Toussaint of Service Publique de Wallonie; Chris Stringer of the British Natural History Museum; and Jean-Jacques Hublin of MPI-EVA.
Posts: 6572 | From: N.Y.C....Capital of the World | Registered: Jun 2008
| IP: Logged |
quote:Originally posted by MindoverMatter718: Such studies add to the growing body of evidence that subtle developmental differences exist between us and our Neanderthal cousins. The recent sequencing of the Neanderthal genome has provided tantalizing genetic clues pointing to differences in cranial and skeletal development between Neanderthals and modern humans ..[...].."These new methods present a unique opportunity to assess the origins of a fundamentally human condition: the costly yet advantageous shift from a primitive 'live fast and die young' strategy to the 'live slow and grow old' strategy that has helped to make humans one of the most successful organisms on the planet," Smith says. Humans' extended maturation may have facilitated additional learning and complex cognition, possibly giving early Homo sapiens an advantage over their Neanderthal cousins.
May explain why Europeans age very badly and quickly, their Nanderthal genes, lol j/k. But nonetheless another addition to the biological differences between modern humans and Neanderthal.
Posts: 6572 | From: N.Y.C....Capital of the World | Registered: Jun 2008
| IP: Logged |
posted
Quite right. The distinctions are striking, if not marked, which makes me wonder what kind of a person would want to be a neanderthal descendant instead of a full-fledged human being, i.e. the African race.
-------------------- The Complete Picture of the Past tells Us what Not to Repeat Posts: 7516 | From: Somewhere on Earth | Registered: Jan 2008
| IP: Logged |
posted
These scientists are just guessing they don't know a damn thing about the Neanderthals.
The whole thing is just a a diss on Neanderthals. What happened was that the Neanderthals were sexier and smarter than the Humans at that that time*, don't believe the negative hype.
So you know what happened? Humans got jealous so we killed them off with clubs.
Now we want to act like they were better than them. Same old story
*keywords "at that time"
Did we ever get to hear the Neanderthal side of the story? what they couldn't talk? you believe these European scientist?
Posts: 42938 | From: , | Registered: Jan 2010
| IP: Logged |
quote:Originally posted by MindoverMatter718: Such studies add to the growing body of evidence that subtle developmental differences exist between us and our Neanderthal cousins. The recent sequencing of the Neanderthal genome has provided tantalizing genetic clues pointing to differences in cranial and skeletal development between Neanderthals and modern humans ..[...].."These new methods present a unique opportunity to assess the origins of a fundamentally human condition: the costly yet advantageous shift from a primitive 'live fast and die young' strategy to the 'live slow and grow old' strategy that has helped to make humans one of the most successful organisms on the planet," Smith says. Humans' extended maturation may have facilitated additional learning and complex cognition, possibly giving early Homo sapiens an advantage over their Neanderthal cousins.
May explain why Europeans age very badly and quickly, their Nanderthal genes, lol j/k. But nonetheless another addition to the biological differences between modern humans and Neanderthal.
What would be a critique of the recent studies purporting to find Neanderthal DNA in modern humans? What are weaknesses or strengths of such studies?
Posts: 5905 | From: The Hammer | Registered: Aug 2008
| IP: Logged |
posted
No critique, if the genes are there they're there. But the only thing I'd say is that it's negligible being that everything amongst anatomically modern humans from brain development (which likely to contribute to cognitive differences between modern humans and Neanderthals), physical development (age slower), cranio-facial tendencies etc... all diverge from that of the Neanderthal.
Posts: 6572 | From: N.Y.C....Capital of the World | Registered: Jun 2008
| IP: Logged |
posted
^^Could the trace elements of such genes be simply so-called "junk" DNA, per the article below? By "junk" DNA they suggest DNA shared between humans and some animals as part of generalized evolution. Could this "junk" pattern be also present in the Neanderthal DNA, more specific to hominids than the generalized "junk" DNA below, but "junk" signatures nevertheless? Not saying it is so, just wondering if the same pattern might apply in a more focused way re Neanderthal-human. ----------------------------------------------------------------
Humans, animals share more DNA than previously thought Santa Cruz study shows common 'junk' fragments
Keay Davidson, Chronicle Science Writer San Francisco Chronicle May 8, 2004 04:00 AM Copyright San Francisco Chronicle. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
The next time you play with a dog or shriek at a mouse or slice into a chicken, keep this in mind: They're your distant cousins, genetically speaking.
New evidence for the unity of earthly life was revealed Thursday by scientists at UC Santa Cruz and elsewhere, who reported discovering a breathtaking number of perfectly matched DNA fragments in these creatures and humans.
What's equally amazing to the scientists is how many of the matching fragments are part of material once scorned as "junk DNA," genetic detritus that has accumulated over the eons and that, it was long assumed, serves no useful purpose.
Now, the evidence of the long-run endurance of so much "junk" suggests that, on the contrary, at least a fraction of the "junk" does serve some kind of evolutionary purpose, although scientists don't know what it is.
A team led by UC Santa Cruz postdoctoral researcher Gill Bejerano used high-speed computers to compare the gene sequences of humans and animals, they report in Thursday's Science Express, a Web site managed by the journal Science.
They found that the chemical sequence of certain segments of DNA in specific vertebrates precisely matches some DNA segments in humans. In all, they identified almost 500 segments that were "completely unchanged" despite tens or hundreds of millions of years of evolution in animals as seemingly unrelated as mice and men.
Metaphorically speaking, it's like finding planks from Noah's Ark in the bulkhead of the Jeremiah O'Brien.
It's hard to understand how the oldest of these DNA fragments -- some more than 400 million years old -- could have endured unchanged over such an incredible length of time, the scientists said. By comparison, the dinosaurs went extinct relatively recently, a mere 65 million years ago.
These DNA fragments "are now evolutionarily frozen. We don't know of a biomolecular mechanism that would explain them," said Professor David Haussler of UC Santa Cruz, a computational biologist who runs the lab where his postdoctoral colleague, Bejerano, did most of the work. The research team also included scientists from the University of Queensland in Brisbane, Australia. Their computer-crunching uncovered 481 matched DNA segments, each of which is at least 200 "base pairs" long. The longest is 800 base pairs. (Strands of DNA are composed of "base" molecules that pair up, forming a continual genetic code that controls growth and activity in virtually all life forms.)
The long-run survival of the genetic segments is especially puzzling because for DNA, time is a ruthless gauntlet. Over the eons, genes routinely suffer mutations caused by accidents, such as when a high-speed space particle or cosmic ray smashes through the DNA coil, or by errors that occur when DNA copies itself.
How could the 481 matching fragments have endured intact for so long and in such widely separated life forms? After all, the human evolutionary line and chicken lines went their separate ways 300 million years ago, while the human and fugu-fish lines said sayonara more than 400 million years ago.
Neo-Darwinian theory holds that genes coding for beneficial traits are more likely to survive because they enhance the organism's chance of survival; those genes that don't enhance survival tend to die out because the organism carrying them is less likely to reproduce.
By this reasoning, Haussler explains, the matching DNA fragments might have been preserved in pristine shape because they serve some useful evolutionary purpose -- its nature still unknown.
-------------------- Note: I am not an "Egyptologist" as claimed by some still bitter, defeated, trolls creating fake profiles and posts elsewhere. Hapless losers, you still fail. My output of hard data debunking racist nonsense has actually INCREASED since you began.. Posts: 5905 | From: The Hammer | Registered: Aug 2008
| IP: Logged |
UBBFriend: Email this page to someone!
Printer-friendly view of this topic