Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.
That's right and matches the headline. But what about the 'ascender' part? Chimps and Orangutan are not our ascenders. If we move through the phylogeny tree, we see the chain of ascenders of modern man: H. erectus < H. habilis < Forest ape. What is older that these forest apes? (if they are extinct). OsmanRF34 (talk) 04:20, 29 July 2013 (UTC)[reply]
I've never heard the term "ascender" used in a biology context either, though I've heard the word many times in a mountaineering context. And yes, for the species immediately preceding any given species in the timeline of evolution, the correct term is "ancestor". 24.23.196.85 (talk) 07:38, 29 July 2013 (UTC)[reply]
So, your question is which is the closest species that has some present day descendants that are humans and others that haven't changed enough to be considered a different species? 202.155.85.18 (talk) 07:29, 29 July 2013 (UTC)[reply]
The answer to that question is; there are no currently known extant species from which humans could have evolved. The oldest known extant species are the tuatara (200 million years old, diverged from synapsids 315 million years ago), horseshoe crab (440 million years old, diverged from deuterostomia 555 million years ago), the coelacanth (400 million years old, diverged from mammalia 555 million years ago), platypus (110 million years old, diverged from primates 220 million years ago) and the lamprey (360 million years old, diverged from mammalia 416 million years ago. Since they all appeared after their phylogeny had diverged from homo sapien's they cannot be an ancestor. 202.155.85.18 (talk) 09:17, 29 July 2013 (UTC)[reply]
The female beauty standards vary across cultures, but I wonder how such criteria as wide hips, thin waist and long legs are transferred to many people seemingly at subconscious level? I know such traits are related to biological advantages, but many people share such notions without even knowing it, so what's the mechanism of transfer? Is it at gene level or something else?--93.174.25.12 (talk) 07:56, 29 July 2013 (UTC)[reply]
Jealousy more or less blindly driven by the urge of competition is certainly one strong influence. You can for example find that same strange behavior of "jealousy about food" among all higher Organisms where one entity tries to get the food of the other no matter an even bigger portion may actually be right in front of its nose. So in consequence whatever features the most dominant or most active male entity makes his choice on all his competitors will adapt to subconsciously. --Kharon (talk) 14:26, 29 July 2013 (UTC)[reply]
When I see areas being defined as having high Endemicism, it is in places far away from where I live (near Washington, DC). Even the few areas in the United States that I've heard of are either on the Hawaii, the West Coast (Spotted Owl/California condor) and Florida. On the other hand, it seems like most of the eastern half of North America is just one large ecological region. So, for the Eastern half of North America north of Florida, are there any mammals, bird, reptile or amphibians whose entire habitat is smaller than a circle one hundred miles across? (This was sparked by a comment that an acquaintance made that "you could pave the entire state of Maryland over and no animal would go extinct")Naraht (talk) 19:35, 29 July 2013 (UTC)[reply]
Travel from Toledo, OH to College Park, MD, and you will cross several ecoregions.Endemism doesn't really say anything about the scale. For instance, we have a list of Endemic birds of eastern North America, which lists several endemic species. But they have decently large ranges, and it seems that you are interested in endemic species that also have very small ranges. For those, in eastern USA, I'd start looking at the New_Jersey_Pine_Barrens, [3], and also the Barrier islands along the coast. There are definitely some endemic and endangered plant spp there. Finally, there are a number of ecoregions in the eastern USA, each with their own plant and animal communities. These regions can have remarkably distinct flora and fauna, though the differences are not always visually striking. SemanticMantis (talk) 20:16, 29 July 2013 (UTC)[reply]
While both the Maryland Darter, the Franklinia (sort of) and the Venus Flytrap qualify, I limited my initial request to Mammals, Birds, Reptiles and Amphibians. I agree with the restatement "it seems that you are interested in endemic species that also have very small ranges", perhaps I should have phrased in in that way. It seems like even the extinct Mammals/Birds of the US East Coast like the Red Wolf and the Carolina Parakeet had relatively *wide* ranges more than 500 years ago. Naraht (talk) 20:43, 29 July 2013 (UTC)[reply]
Birds and mammals don't tend to have such small ranges in areas like the Eastern US with large contiguous ecological regions. It's not like there are deep mountain valleys or flightless birds on offshore islands. If I remember correctly, the completeion of Route 18 in New Jersey was delayed by some sort of herp. But I cannot recall the exact species. μηδείς (talk) 21:02, 29 July 2013 (UTC)[reply]
An interesting perspective on this very problem can be found in 1493: Uncovering the New World Columbus Created, which discusses the way in which human migration (via the so-called Columbian Exchange) has created ecosystems which are much larger and more homogeneous across wider areas of the Earth's surface. The author even coins a term "Homogenocene" to represent the current ecological age as a break from the Holocene epoch, considering this trend. I can't say one way or another how "correct" this view is, but it is an interesting perspective. --Jayron3223:39, 29 July 2013 (UTC)[reply]
Can mathematical models cause errors in astrophysics
I know when astronomers and planetary scientist tries to predict future events of solar system and stars they typically use mathematical models and physical laws. Is mathematical models and astrophysical law equations always a reliable predictions, or mathematical models can often be wrong? I saw [4] when calculating remaining planets around white dwarfs, they use mathematical models and physical laws. I thought mathematical models and physical law/equations has to make reliable predictions, or they are nothing more than a basketball shot.--69.226.33.213 (talk) 20:32, 29 July 2013 (UTC)[reply]
Well models are not reality. They will be making huge simplifications. There is also the possibility that there is an error in the interpretation of what is happening. So the model does not apply. Lastly, errors can increase over time so making future predictions less and less accurate. For example this happens in weather forecasting. Predicting the future positions of the planets gets less and less accurate over long periods of time too. Graeme Bartlett (talk) 21:33, 29 July 2013 (UTC)[reply]
If you want to "predict" there is already some unknown factor or even an chaos element in it and its not the mathematical method causing an error instead your expectation of the capability of that method is wrong. You can be certain that a position of an known Planet can be calculated very exactly thousands of years into the future but you cant calculate how strong the solar wind will be around Earth next week. --Kharon (talk) 00:10, 30 July 2013 (UTC)[reply]
So these math problems only gives us the estimates but not the exact variable? So we won't know where the habitable zone in 7 billion years future until somebody can actually try to find the habitable zone around giant star? Have anybody really tried to find habitable moon/planets around giant star. So the mathematical formulas will only give me the guesses and is rather waste of time until better studies are done? --69.226.33.213 (talk) 01:43, 30 July 2013 (UTC)[reply]
Read the section you referred to. It applies to "an idealized object which is perfectly opaque and non-reflecting". The sun is not a perfect black body, so any results you obtain with the equation will not perfectly describe the behavior of the sun. In physics teaching, this is often joking referred to as "Assume a perfectly spherical cow of uniform composition existing in a perfect vacuum", which, believe it or not, we even have an article about: Spherical cow. No, models are not useless, and they are much better than mere guesses, but they do have their limitations. Dominus Vobisdu (talk) 06:01, 30 July 2013 (UTC)[reply]
One of the most noticeable differences between an amateur and a professional scientist is that the professional knows when to place stock in a particular model. This is a skill that develops with experience, and perhaps is augmented by some innate aptitude. Amateurs blindly "plug and chug," and will spit out any result of any equation, without any understanding of why they are using that equation.
Specifically regarding error in equations: entire branches of applied mathematics - like sensitivity analysis - are dedicated to the study of how much error is introduced if a particular input is wrong. Statisticians use confidence intervals and other probabilistic measurements to describe reliability of data. Engineers and experimental scientists use signal to noise ratios to express how imperfect any part of their measurements are. So, error can be quantifiable. If we assert with high confidence that all our errors are small, we can be very accurate. Again, a distinction is that a professional scientist should be better at ensuring that they accounted for everything. Occassionally, they screw up; eventually, if the screw-up is big enough, somebody else catches it and fixes it. Nimur (talk) 14:25, 30 July 2013 (UTC)[reply]
Also, when I was a student, a Prof. told us in the very first astrophysics lecture that in many cases it is good enough to be within a factor ten of the correct answer. This has to do with the type of questions one wants to be answered in astrophysics as opposed to theoretical physics. In recent years things have changed in this field, but there is still some truth in it.Count Iblis (talk) 14:32, 30 July 2013 (UTC)[reply]
The reliability of mathematical models critically depends on the nature of what is being modeled. In the case of a planet in it's orbit, there are hardly any unexpected events that can cause significant deviation from idealized behavior - and small errors in our measurement of the initial position and velocity don't get wildly magnified as the model runs off into the future. Contrast that with systems like weather and solar wind - which are chaotic systems (in the mathematical sense of "chaos theory") where the smallest error in initial conditions or the smallest error in the model will rapidly blow up into huge errors. That's "the butterfly effect" - and explains why weather forecasts for more than a few days into the future fare no better than chance but the position of a large moon or planet can be known to high precision over a period of hundreds of years. SteveBaker (talk) 14:35, 30 July 2013 (UTC)[reply]
And even something as seemingly stable as the solar system is not necessarily stable in the very long term - see n-body problem and stability of the Solar System ... "an error as small as 15 metres in measuring the position of the Earth today would make it impossible to predict where the Earth would be in its orbit in just over 100 million years' time". Gandalf61 (talk) 15:53, 30 July 2013 (UTC)[reply]
Yes - but over 100 million years, unknown factors such as the fate of the sun and the consequent variation in the pressure of the solar wind and such mean that we don't know the position that the earth will be at, even if we had it's current position accurate to a nanometer. SteveBaker (talk) 20:27, 30 July 2013 (UTC)[reply]
The question of the stability of the solar system can be investigated. Recent studies have come up with surprising results, see e.g. here:
"These results also answer to the question raised more than 300 years ago by Newton, by showing that collisions among planets or ejections are actually possible within the life expectancy of the Sun, that is, in less than 5 Gyr. The main surprise that comes from the numerical simulations of the recent years is that the probability for this catastrophic events to occur is relatively high, of the order of 1%, and thus not just a mathematical curiosity with extremely low probability values. At the same time, 99% of the trajectories will behave in a similar way as in the recent past millions of years, which is coherent with our common understanding that the Solar System has not much evolved in the past 4 Gyr. What is more surprising is that if we consider a pure Newtonian world, the probability of collisions within 5 Gyr grows to 60 %, which can thus be considered as an additional indirect confirmation of general relativity." Count Iblis (talk) 21:07, 30 July 2013 (UTC)[reply]
This IP editor has been asking essentially the same question about mathematical models over and over again for months, and getting essentially the same answers each time. I don't get it. Looie496 (talk) 15:31, 30 July 2013 (UTC)[reply]
Or maybe I can think about comparing astrophysics and professional scientist to predict traffic light evolutions in Orange County in the future. Ever since I was tens of years old, I have tried to predict what will the traffic lights in Irvine Base Areas will happen 6-10 years in the downtime. I noticed the specifications of red, yellow, and green bulbs changes overtime, and the traffic inspection paints happens on traffic light enamel. I could have tried to do models I just didn't have that time to do that and I am kind of lazy to do that. First, models have to be consistent and has to work on many conditions. Few years ago, most South Orange County cities still didn't have incandescent yellow light bulb replaced, only the reds and greens were replaced around 2001-2002 areas [5] I was expecting the yellow light specifications will be the amber LED colorings, but some of the cities post 2010 actually came out to egg-yellow LED lighting the new LED standards, and between 2011-2012 City of Irvine went ahead, replaced some obsolete red, yellow, green bulbs with newer systems scarlet-red, lemon-yellow, cyan-green according to the metric table listing. I can learn, when I try to create model to predict what will the traffic light bulbs will happen 5-10 years in the future, each time things actually presents and performs, my older speculations becomes more and more inaccurate. Without calling the city department to ask them questions, I can try to create a model templates according to what I have studied in the past if I have time to do that, but the problem is the models have to be consistent, and has to work to all-related cases it is hard to do because I have to organize informations, predictions intersections undergoing constructions usually happens to cause replacement of signal poles, (same as what happened on Culver and Walnut Avenues in Irvine two years ago) requires depth understanding and enough studies to be done to imitate like-intersections undergoing construction, but each time newer inventories comes up without even knowing it.--69.226.33.213 (talk) 00:58, 31 July 2013 (UTC)[reply]
My $0.02, nothing is infinitely correlated or infinitely predictive, and this has nothing to do with the correctness of a model. If I take a baseball and throw it in the air, I can use projectile motion to calculate its position and velocity 15 or so seconds later, and assuming that there are no confounding variables the result should be highly predictive. Now if I try and rely on the same model to tell me where that baseball will be several minutes from now than it becomes a bit more difficult, taking it to the extreme if we try to figure out where it will be a million years from when I first tossed it in the air, the best you could do would be to say that it's most likely somewhere in the general vicinity of earth. This doesn't mean that there's no such thing as projectile motion. See also correlation function. (+)H3N-Protein\Chemist-CO2(-)11:25, 31 July 2013 (UTC)[reply]
