Talk:Timeline of evolution
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Lungs from swimbladders?
shit
I thought the general consensus was that swim bladders evolved from lungs, or at least that a generic swim-bladder-lung is ancestral to both?
See e.g. Wikipedia swim bladder article (http://en.wikipedia.org/wiki/Swim_bladder) and [http://www.britannica.com/eb/article?eu=120748 "Fish." Encyclopędia Britannica. 2004. Encyclopędia Britannica Premium Service. 27 Aug. 2004]
kYA instead of TYA ?
I'd like to change the notation slightly to be more in line with SI standards. In particular, I'd like to use kYA instead of TYA.
Are there any objections?
- Works for me, do it! -Vsmith 16:41, 22 Nov 2004 (UTC)
There's this statement:
Neanderthal man (Homo neanderthalensis) makes magic, bury the dead and care for the sick.
Burying the dead is deducible from finding graves, care for the sick is deducible from the bones of injured individuals who couldn't have survived unaided. But where does the statement they practiced magic come from? (There's nothing about this on the Neanderthal page) I suppose burial itself might be considered a magical act, but that's not what we today generally call magic.
Magic
Burial in modern times are associated with religion and rituals. The magic here probably refers to such rituals and a belief in after-life, precursors to modern religion.
60 kYA ?
What about the events 60kYA and 150kYA ? Is it a joke or something ?
- Not jokes, but actual scientific results obtained by comparing the genetic material of a wide selection of modern humans. The numbers come from biological measures of inbreeding.
- Since female humans have no Y chromosome (except in a few rare instances which I'll ignore), Y's are only inherited from men, and there's no (or very little?) mixing of genetic material. If you have a Y, you got it from your dad. The only way to change the Y is to have a mutation. Since mutations occur at a known, (approximately) constant rate counting up the number of mutations necessary to cover all modern variants of the Y chromosome gives the amount of time which has passed since the life of the last male ancestor of all living human males. See [1] (http://john.hynes.net/y.html) and Y-chromosomal Adam.
- You can do something similar to calculate the age of the last female ancestor of all living humans. The mitochondria in your cells has a different set of genetic material from the cells / cell nuclei themselves. Your mitochondria come only from your mother since a sperm carries its mitochondria at the base of its tail - which is shed at fertilization. The zygote thus retains mitochondria only from the ovum. Analyze a large sample of mitochondria extracted from the cells of many different people of different ethnic groups to get an estimate of the number of mutations that have occurred and you can calculate the age of everyone's great-great-great-...-great-grandmother. See [2] (http://www.geocities.com/krishna_kunchith/misc/eve.html) and Mitochondrial Eve.
- Scientists have named the two individuals described above as Adam & Eve, although there were older humans and the two people didn't coexist. Incidentally, you could probably do something similar to determine the age of the last common ancestor of humans & chimpanzees, humans & new world monkeys, humans & dogs, etc. You'd run into trouble at some point, though, since the mechanisms of reproduction vary somewhat between species and I'm not sure how much you have to assume about the age at which reproduction happens. SMesser 17:54, 7 Jan 2005 (UTC)
- Y-chromosomal Adam was not "the last male ancestor of all humans alive today." He was the last male-line-only ancestor of all humans alive today. They are two different concepts.
- For example, the last male ancestor of me and my cousin Aaron is our maternal grandfather. (His mother is my mother's sister). But I am not closely related to his father, nor he to mine, so our last male-line-only (Y-chromosomal) ancestor, tracing back through our fathers and our father's fathers etc., lived much further back in time. --Cam 15:36, Apr 16, 2005 (UTC)
self-reproducing RNA molecules?
Is there an evidence for that? I mean, do we have the kind of evidence on this as we have on -for example- the first lifeforms found on earth? If there is, it's not mentioned in the RNA world hypothesis article, which I find very strange. If wikipedia does indeed maintain a NPOV, this should really not be in the article. It does, however say that this theory -at least in it's present state- is very improbable.
- The evidence is admittedly scant. But then, the first lifeforms on earth to leave fossils were fairly complex. Bacteria, viruses, prions are all fairly simple critters, but don't generally leave fossils the way things with hard shells / bones do. The first lifeforms were probably even smaller and simpler. Talk.Origins[3] (http://www.talkorigins.org/faqs/abioprob/abioprob.html) has a nice, detailed discussion of the stages between no life and life as we know it, as well as a set of technical links to many of the stages, including the RNA world hypothesis. That Wikipedia article also has several external links supporting the hypothesis.
- In the interest of brevity, I'd rather not have external links at every stage of the Timeline of evolution page. For this entry, I think links to RNA world hypothesis and Origin of life are sufficient. Since it is a hypothesis (rather than a leading theory) with only scant evidence, I think the word "possibly" is essential. I've also deleted the word "first" since the boundary between auto-catalyzing (or mutually-catalyzing) chemical reactions and actual life is vague, and the RNA world might have been one of the later stages of abiogenesis.
- If you'd rather replace the RNA world entry on Timeline of Evolution with something else, I'll be satisfied as long as the new entry reflects an intermediate stage of abiogenesis the mainstream science community considers somewhat plausible.SMesser 17:41, 24 Mar 2005 (UTC)
- My only concern is -even though the article does say "probably"- that the scientific community only accepts abiogenesis as a basis for a lack of better explanation. Now, I might sound like a creationist nut for saying this, but I don't think we should accept this as a valid standpoint. If we do, however, we should provide links to all theories about the origins of life (even non-scientific ones, since at this stage, science simply cannot provide a good answer to that question), or -preferably- none at all. My point is, that right now this is a matter of belief (in the non-religious meaning of the word).
- I'm really hoping that this suggestion won't start a creationist-abiogenesist flamewar.
- AndrasGerlits 11:06, 26 Mar 2005 (UTC)
- First things first - you can use a sequence of four tildes (~) to sign your posts. Added benefits include a nifty timestamp and a link to your talk page (where you can get & respond to messages that might not be interesting to the broader community). It also helps readability when multiple people are discussing something.
- Second, evolution is a scientific term and theory, so Timeline of evolution should emphasize the scientific standpoint. As a scientist (Ph.D. in plasma physics), I am personally biased in favor of giving the scientific POV as much screen space as possible. I'll try not to let that get in the way of writing NPOV articles.
- There are several points of view which may not be scientific, but which are completely valid from a religious / philosophical point of view. I'd put creationism & intelligent design in that category. Science is as much a philosophy and a problem-solving / technology-building tool as anything else. Maintaining NPOV probably means we should make at least passing reference to those on anything as contentious as the origin of life.
- Getting back to the specific topic, I'd rather not list all the different ideas floating around about how life got here. Crossing the "genes-first" and "metabolism-first" models with the four location models (ocean, clay surfaces, deep subterranean, and extraterrestial), we get eightvery broad scientific hypotheses, each with its own proponents, weaknesses, sub-categories, etc. We shouldn't spend the time to outline each of them here. That's what the link to origin of life is for. The various creationist models show a similar variety in the level of divine intervention, the age of the universe, and the way in which creation happened. Creation vs. evolution debate outlines a number of additional ideas which don't fit neatly into either of the above categories.
- I'm horrible at brevity.
- I'd also argue that the scientific community has more to support their ideas of abiogenesis than a lack of a better explanation.
- Anyway, what do you think of the following entry:
- 4000 MYA | Life appears, probably in some form much simpler than any modern cell. See origin of life. The atmosphere doesn't contain any free oxygen
- If absolutely necessary, we could put some link to creation vs. evolution debate at the top, although I think the contextual link to evolution and the links on origin of life are sufficient. Timeline of evolution isn't a stand-alone page, so we don't need to link in as much stuff directly.SMesser 22:46, 25 Mar 2005 (UTC)
- I'm very much impressed by your constructive approach to my suggestion. Yes, I do think that the sentence you're proposing is a step in the right direction, and would be glad to see those changes. However, I think you're confusing science with materialism, a misconcept shared by many. I still believe that the scientific approach (which is the only true NPOV) would be not to mention even abiogenesis (note, I'm not saying we should give any explanation to the origins of life on earth), since that's a materialist dogma (since it's a philosophy, not a methodology) and not a scientific fact. AndrasGerlits 11:06, 26 Mar 2005 (UTC)
What's wrong with the use of materialism in science? I thought this is the ONLY way to do science?
- Science does not equal materialism. Science is a methodology designed to use our senses when analysing our environment, any scientific theory must adhere to the scientific_methods, some of which abiogenetic theories clearly do not. For example, they cannot be falsified. Materialism on the other hand, is a philosophy, a certain belief in the way the universe works, when certain thing are assumed without needing any proof. Nothing is taken for granted in the natural sciences. AndrasGerlits 11:52, 30 Mar 2005 (UTC)
Then what is material science?
- You're joking with me, right? Also, what's that new stuff about the self-replicating molecules? This section is getting worse by the minute. We should just get rid of the whole thing. AndrasGerlits 08:57, 2 Apr 2005 (UTC)
Tunguska event removed from timeline
I removed the Tunguska event from the timeline, because it has absolutely nothing to do with the evolution of life on Earth, nor did it have any significant effect on the Earth itself. 157.181.71.7 06:07, 19 Apr 2005 (UTC)
Tunguska event
I added the Tunguska event just to remind our human readers that collision with Near Earth Objects have always been happening. I have not even included the near-misses discovered in recent years. Flattening 2000 square km of forests to me is quite a significant change to earth and might have caused certain species(though not human) to be extinct. It all depends on your perpectives. It seems that smaller collisions are more frequent than bigger ones , which really change the course of evolution. We ourselves have a real possibility of following the footsteps of the dinosaurs. Such catastrophe really put man's ego in their humble and correct place.
Evolution is at best a Theory
It's nice to think about how and why we exist on this planet but at best, these thoughts that we as individuals have, can only be answered with a philosophical answer. Let's face it, we all live with a philosophy of life. Some have bought into this notion that in the THEORY of Evolution, life sprang forth from non-living material, which was given the exact conditions it needed for this to occur.
Before you even begin to entertain this idea, I would ask you to think about this one thing. Where did the information come form in order to have life in any form, exist under any condition?
I would suggest that evolution and the theories thereof, is more closely related to a religion by which great faith must be exercised in order to explain that which is not subject to real science scrutiny of the ideas and theories that are not able to be observed and or duplicated in a laboratory.
So before any further meaningful discussion about evolution can be explored, lets have a moment to examine our motives for wanting to adhere to this theory and in that, present it as such....just another theory to try and bring meaning to our lives. For if all it does is to explanation our being, then what real purpose does it serve in our fragile humanity.
Regards, B.E.
What do you mean?
You seem to be self-contradicting. You begin by saying that the question of life should best be answered by philosophy and yet when you examine evolutionary theory you advocate the use of labaratory work. What are you trying to say?
Lemurs
In the timeline Lemurs seem to have moved from Africa into Madagascar 64MYA and 40someting MYA. Was it a long crossing or did they do it twice, or is one crossing to be removed?
Anthropoids
An anon just added this:
- Anthropoids : Bugtipithecus inexpectans, Phileosimias kamali and Phileosimias brahuiorum similar to today's lemurs , lived in rainforests on Bugti Hills of central Pakistan
"Bugtipithecus inexpectans" and "Phileosimias brahuiorum" each only get one google hit, to the same page from a non-English website, [4] (http://info.onet.pl/1105435,16,1,0,120,686,item.html). "Phileosimias kamali" gets me no hits at all. Can anyone confirm this info. func(talk) 06:42, 1 Jun 2005 (UTC)
1. Ice Age/isthmus 2 Homo chokepoint
1) Neither here, nor Wiki entries on the ice age I found, discuss the idea that the raising of the Isthmus of Panama [mentioned here] is the ultimate beginning of the global thermohaline circulation, which in turn led to the ice ages. Many think adaptation to the resultant chaotic climate is what drove human evolution over that tiime period. Worth a mention?
2) Toba volcanic eruption at 74 KYA. I've seen the human "chokepoint" population mentioned in several places at circa 10,000, nothing close to 2,000. Consider using a range.
It's great to see all this timeline in one digestable piece!
Skookum172.193.251.124 17:55, 3 Jun 2005 (UTC)