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Natural Science Forum / Biology / Paleontology / September 2004Date Estimates...
I was recently corrected on a date I posted in this NG. I've collected miscellaneous dated events from here, news articles, etc., and would appreciate any feedback (corrections, omissions of "major" events, etc.) on the following list: Years Ago - 4.2B - 3.5B - Life begins (1st Prokaryotes - bacteria/stromatolytes) - 3.1B - earliest photosynsthesis (oxygen, extinction of anaerobes) - 1.2B - earliest eukaryotes (protists) - 1.1B - .8B - multicellularity arose - 530M - 505M - Cambrian explosion (all major extant body plans + more) - ~490M - Jawless fishes appear - 460M - Fungi & green plants migrate from sea to land - 420M - Jawed fishes appear (True fishes not until 345MYA) - 300M - Reptiles appear, as well as insects - 246M - First non-insect creatures on land (+/- 2MY) - 220M - 65M - Dinosaurs reign until K/T event (Chicxulub) - 210M - Now - Mammals; these remained small until after K/T - 135M - Flowering plants appear - 55M - 45M - "Precetaceans", early cetaceans appear - ~56M - Pre-primate with opposable big toe - ~35M - First ape-like creatures appeared (Unclear on "apelike".) - 9M(+/- 3M) - Major split later evolving into: 1. apes and 2. humans - 7.0M - Sahelanthropus tchadensis (maybe 6.5 - 7.0 mya) - 6.0M - Orrorin tugenensis Biped - 5.0M - Kenyanthropus platyops (Sci. Am. places this ~ 3.5M) - 5.8M - 5.2M - Ardipithecus ramidus kadabba - 4.5M - 1.0M - Australopithecines (tree even bushier than genus Homo) - 2.5M - Now > Genus Homo (rough breakdown below... ) 2.5M - 1.7M - Early genus Homo (incl. H. habilis, H. rudolfensis) 1.8M - .1M - Homo erectus (incl. H. ergaster) .8M - .1M - Archaic Homo sapiens (incl. H. heidelbergensis) .3M - 30K - Pre-Neanderthal / Neanderthal (H. neanderthalensis) .16M - Homo sapiens idaltu .13M - Now - Homo sapiens sapiens (Modern Humans) I'd also be interested in knowing, briefly, the differences between jawed fishes (420mya) and true fish (345mya), as well as apelike (~35mya) vs. apes. TIA. Regards, Brett. > I was recently corrected on a date I posted in this NG. I've collected > miscellaneous dated events from here, news articles, etc., and would > appreciate any feedback (corrections, omissions of "major" events, etc.) on > the following list: A lot of these are open to all sorts of definitional ambiguities. Others are subject to big holes in the available data. Some are estimates, othrs are daes of the oldest known fossil, which must be younger than the true date of origin. Etc. You also show why it's good to use stratigraphic units instead of absolute time units. It's possible that the estimated date of the end-Permian extinction may change, but it will always be at the end of the Permian. > Years Ago > - 4.2B - 3.5B - Life begins (1st Prokaryotes - bacteria/stromatolytes) [quoted text clipped - 4 lines] > - 530M - 505M - Cambrian explosion (all major extant body plans + more) > - ~490M - Jawless fishes appear What's a jawless fish? Would, e.g. Haikouichthys count? Anatolepis? A conodont? This date seems to be based on something like Sacabambaspis, say mid-Ordovician (though that date is now right at the beginning of the Ordovician). > - 460M - Fungi & green plants migrate from sea to land > - 420M - Jawed fishes appear (True fishes not until 345MYA) That would be mid-Silurian. The oldest acanthodians would fit that general time-frame. The latter date is mid-Carboniferous. I don't know what it's talking about, unless it's talking about the actinopterygian crown group, which would be around that time. I have no idea what "true fishes" would mean. > - 300M - Reptiles appear, as well as insects That's late Carboniferous. Possibly a reasonable date for reptiles, about right for Hylonomus, but totally wrong for insects. > - 246M - First non-insect creatures on land (+/- 2MY) Wherever did that come from? That date would be in the Triassic. And it contradicts several of the others. > - 220M - 65M - Dinosaurs reign until K/T event (Chicxulub) The oldest known dinosaur is around 228ma: Eoraptor or Herrerasaurus. > - 210M - Now - Mammals; these remained small until after K/T Late Triassic. OK, depending on what you call a mammal. > - 135M - Flowering plants appear > - 55M - 45M - "Precetaceans", early cetaceans appear > - ~56M - Pre-primate with opposable big toe > - ~35M - First ape-like creatures appeared (Unclear on "apelike".) This would be early Oligocene. Seems very early to me. Generally, mid-Miocene is the age given for the earliest apes. > - 9M(+/- 3M) - Major split later evolving into: 1. apes and 2. humans This makes no sense, since some apes are more closely related to humans than other apes are. > - 7.0M - Sahelanthropus tchadensis (maybe 6.5 - 7.0 mya) > - 6.0M - Orrorin tugenensis Biped [quoted text clipped - 12 lines] > I'd also be interested in knowing, briefly, the differences between jawed > fishes (420mya) and true fish (345mya), No idea what "true fish" means. > as well as apelike (~35mya) vs. > apes. TIA. Regards, Brett. No idea. Hi, John, and thanks. > > I was recently corrected on a date I posted in this NG. I've collected > > miscellaneous dated events from here, news articles, etc., and would [quoted text clipped - 10 lines] > end-Permian extinction may change, but it will always be at > the end of the Permian. Point taken - I'll try to get used to these. > > Years Ago > > - 4.2B - 3.5B - Life begins (1st Prokaryotes - bacteria/stromatolytes) [quoted text clipped - 9 lines] > say mid-Ordovician (though that date is now right at the beginning of > the Ordovician). I understand a jawless fish of today to be a lamprey, for example. From the number of times I've read of them, I thought it to be a fairly unambiguous term (sigh!). > > - 460M - Fungi & green plants migrate from sea to land > > - 420M - Jawed fishes appear (True fishes not until 345MYA) [quoted text clipped - 9 lines] > That's late Carboniferous. Possibly a reasonable date for reptiles, > about right for Hylonomus, but totally wrong for insects. I've also read ~400MYA for insects... would that be "better"? > > - 246M - First non-insect creatures on land (+/- 2MY) > > Wherever did that come from? That date would be in the Triassic. And it > contradicts several of the others. My notes aren't alway consistent. It came from a 2002/08 article, but I didn't note the source (The Enquirer? - just kid'n). In what context does it contradict several of the others (aside from reptile)? (My original notes said "(fishlike) creature" which I omitted for brevity.) > > - 220M - 65M - Dinosaurs reign until K/T event (Chicxulub) > [quoted text clipped - 16 lines] > This makes no sense, since some apes are more closely related to humans > than other apes are. OK. > > - 7.0M - Sahelanthropus tchadensis (maybe 6.5 - 7.0 mya) > > - 6.0M - Orrorin tugenensis Biped [quoted text clipped - 18 lines] > > No idea. Again, thanks for the input. Regards, Brett. > Hi, John, and thanks. > [quoted text clipped - 32 lines] > number of times I've read of them, I thought it to be a fairly unambiguous > term (sigh!). Sadly, no. "Jawless" is, but "fish" is not. >>>- 460M - Fungi & green plants migrate from sea to land >>>- 420M - Jawed fishes appear (True fishes not until 345MYA) [quoted text clipped - 11 lines] > > I've also read ~400MYA for insects... would that be "better"? As far as I know, the oldest known insects are from the Rhynie Chert, which is Early Devonian. 400ma would not be a bad estimate of its age. >>>- 246M - First non-insect creatures on land (+/- 2MY) >>> [quoted text clipped - 5 lines] > it contradict several of the others (aside from reptile)? (My original > notes said "(fishlike) creature" which I omitted for brevity.) You're right, it only contradicts that one. However, it contradicts reality by a huge margin. I would suspect either a typo in the original or a copying error on your part. >>>- 220M - 65M - Dinosaurs reign until K/T event (Chicxulub) >>> [quoted text clipped - 48 lines] > > Again, thanks for the input. Regards, Brett. <snip> > >>>- 246M - First non-insect creatures on land (+/- 2MY) > >>Wherever did that come from? That date would be in the Triassic. [quoted text clipped - 7 lines] > reality by a huge margin. I would suspect either a typo in the original > or a copying error on your part. So for: - First non-insect (i.e. fishlike) creatures on land What would be a more reasonable date, and stratigraphic unit for that matter? TIA. Regards, Brett. > <snip> > > >>>- 246M - First non-insect creatures on land (+/- 2MY) [quoted text clipped - 15 lines] > What would be a more reasonable date, and stratigraphic unit for that > matter? TIA. Regards, Brett. I've found one article claiming 360MYA... "Acanthostega was a tetrapod, too, but at 360 million years old, it has a special distinction: aside from creatures suggested by a few older fossil fragments, it is the most primitive tetrapod known. " From: http://www.findarticles.com/p/articles/mi_m1511/is_n6_v16/ai_16951786 >><snip> >> [quoted text clipped - 26 lines] >>What would be a more reasonable date, and stratigraphic unit for that >>matter? TIA. Regards, Brett. I presume you really know that most non-insects are not fishlike either. What you're asking about is the first land vertebrate. > I've found one article claiming 360MYA... > [quoted text clipped - 3 lines] > > From: http://www.findarticles.com/p/articles/mi_m1511/is_n6_v16/ai_16951786 That's Acanthastega. Now we get into questions about what counts as a land vertebrate. Acanthastega had legs, but there's considerable doubt that it ever lived on land. You need to find better web references. Perhaps you could try UC Berkeley's evolution pages. > You need to find better web references. Perhaps > you could try UC Berkeley's evolution pages. Thanks for this, John. It's a great source for pointing out just how little I know :-) If you have any other good ones up your sleeve, I'd appreciate those too. Best regards, Brett. John (or anyone else): > > Hi, John, and thanks. > > [quoted text clipped - 15 lines] > As far as I know, the oldest known insects are from the Rhynie Chert, > which is Early Devonian. 400ma would not be a bad estimate of its age. Looking at the UC Berkeley pages you suggested, John, I came across the following: "Life began 3.8 billion years ago, and insects diversified 290 million years ago" at http://evolution.berkeley.edu/evosite/evo101/IIE1Whathappenedwhen.shtml And at http://www.fossilmall.com/Science/GeologicalTime.htm , the text says insects appeared between 410 and 360 MYA (Devonian). Are these "discrepancies" just the result of unknown/controversial dates, or did it take many tens of millions of years from the time insects arose (~400 in the Devonian) to when they diversified (290 in the Pensylvanian)? (I presume the former.) Also, is there a concensus as to how firm UC Berkeley's OOL at 3.8 BYA (I've read from 3.5 to 4.2)? Regards, Brett. > John (or anyone else): > [quoted text clipped - 35 lines] > the Devonian) to when they diversified (290 in the Pensylvanian)? (I > presume the former.) No, the latter. This of course depends on believing that the fossil record is a reliable guide to the diversity of the insects, which is probably a bad assumption. But the fossil record of insects doesn't become highly diverse until the Pennsylvanian. > Also, is there a concensus as to how firm UC Berkeley's OOL at 3.8 BYA (I've > read from 3.5 to 4.2)? I have no idea where the 4.2 number comes from. 3.5by is presumably taken from the earliest claimed fossils. 3.8 is taken from "chemical fossils", i.e. indirect signs that life may be present. Nothing here is really firm. |
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