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- Lab 8 Notes Fall 1997 The Genus Homo Lab 8 Homo habilis. Homo rudolphensis, and Homo erectus The purpose of the Lab Lab 8 will look at how to distinguish early species of our Genus (or family). Humans are in the Genus Homo and are generally distinguished by their tool use and skeletal features from the Australopithecines and Paranthropines. Homo habilis Homo habilis refers to "Handy Man" and is the first member of the Genus Homo or stone tool manufacturing hominids (even chimps use stone tools) KNM-ER 1813 is Homo habilis. You need to remember the number 1813. KNM refers to "Kenya National Museum" and ER refers to East Lake Rudolph (Now renamed to Lake Turkana) Homo rudolphensis KNM-ER 1470 refers to Homo rudolphensis and dates to 1.9 mya. You need to remember the number 1470. Again: KNM refers to "Kenya National Museum" and ER refers to East Lake Rudolph (Now renamed to Lake Turkana) where the fossil was found by Louis Leakey’s team. Homo rudolphensis evidence of manufacturedstone tools have been found with its remains. Homo rudolphensis existed 2.4 mya. The question for the lab. Q: Is ER 1470 a different species altogether that should be called Homo rudolphensis or is it a Homo habilis? The purpose of this lab is to get you to think about how do you decide if you are looking at 1 or 2 species. A species can successfully mate and produce fertile offspring. You are working with skulls (and obviously fossilized skulls don’t mate). Question? How different do 2 fossils have to be in order to be assigned to 2 different species? Living primate species must serve as the bases to estimate the variation within a species. Gorillas are the most sexually dimorphic humanoid. Does Sexual dimorphism account for the differences in size? In Homo habilis the most significant source of variation to be considered could be sexual dimorphism. Norm of reaction could also play a part. (e.g. less food may result in smaller individuals). is so much larger than 1813 that it is reasonable to assume one is a male and the other a female IF they belong to the same species??? The Short Take Home Quiz The Question: Some argue in favor of classifying 1813 as Homo habilis and 1470 as Homo rudolphensis. Are they justified? Do the data suggest 2 different species of early Homo? Why or why not? Use statistical and comparative data from your lab in support of your argument. A Short Take Home Quiz Due next lab. One paragraph long (1/2) page. Take a position in the first sentence and present your evidence in 3 to 5 sentences. See page 17. Use the statistical and comparative skull data from this lab to support your position. Things to remember Early Genus Homo species generally had larger brains and more human-like teeth than australopithecines. Page 2 of the lab manual describes the three species of Homo habilis, Homo rudolphensis, and Homo erectus. Homo erectus Some H. erectus had a sagittal keel. Homo erectus made Acheulian hand axes and was the first to use fire. Homo erectus was the first to spread out of Africa and all over the world. Homo erectus had a pentagonal shaped skull and a bigger brain. There was much regional variation in Homo erectus skulls. How do you decide if you are looking at 1 or 2 species? The approach to distinguishing 2 fossilized species is based on the idea of "What is an acceptable range of variation in skeletal characteristics for defining 2 skulls as 2 different species?" To do this you need to be able to make a simple graph and use simple statistics. (Remember: Statistics are your friends!) How to do measurements P.9 Facial Height = from the gap in the front teeth (think of David Letterman’s gap in his teeth) to the point between the eyes where the eyebrow ridges come together. Length of the cranium = From between the eyes to the farthest point at the back of the skull. How to do measurements P. 9 Width of the molar = measure from the cheek side of the second molar (M2) to the tongue side of the second molar (M2). Facial breadth (upper) = from the widest part of the eye orbits. Facial breadth (lower) = from the left side of the zygomatic arch (the zygion) to the right side of the face (the zygion). If it is missing, estimate its position. Relative data (you just eyeball it without measuring it) Which skull is more prognathic (which lower face juts out more)? Which has bigger brow ridges? (robust supraorbital ridges)? Which has a deeper "dip" behind the brow ridges (the supraorbital sulcas)? What is the shape of the cranium? Egg shaped? Widest at the bottom? Relative data How much does the skull look egg shaped when viewed from the top? (How much of a post-orbital constriction does it have?) How big is the nuchal area (where the neck muscles attach to the skull)? What is the cranial volume of the skull? Keep sexual dimorphism in mind!!! Relative Data The occipital angle is the angle from the back of the occiput to the nuchal area. It is angled on Homo erectus and fairly flat on Homo habilis and a modern Homo sapiens. The skull first elongated and then went upward over time. Homo erectus had thick skulls and shovel shaped incisors more like our teeth. Terms to know: Statistics A Graph: is plotting data on a piece of paper. The X and Y axes are on each side of the graph. The mean is just the average. You add up (sum) the numbers and divide them by the number of numbers you added together. Statistics terms to know The range of a trait just means the difference between the maximum value and the minimum value. A measure of the amount of variablity surrounding the mean or average of the distribution is called the standard deviation Statistics terms to know Standard Deviation Step 1: To calculate the standard deviation you calculate the mean (average) by adding and dividing by the number of numbers. Step 2: You want to calculate how much each of the measurements differs from the mean so you subtract the mean from each of the measurements (some of these will be negative numbers and some positive). Calculating the standard deviation Step 3: Next you square the deviations. Step 4: Then add the squares together and divide by N (the number of measurements). Step 5: Then take the square root of that number and that is the standard deviation. Standard deviation measures variability. The coefficient of variation (C.V.) The coefficient of variation helps to correct for a small sample size. You divide the standard deviation by the mean and convert the result to a percentage. Biologists want the range of variation within the same species to have a C.V. of around 10% or less. Coefficient of Variation The coefficient of variation is useful if you consider that sexual dimorphism will cause differences in individuals and when you consider how humans vary within our species Humans actually vary by about 15% so 10% is pretty conservative for considering 2 different fossils to be within the same species. Homo erectus Viewed from the back Homo habilis is widest at the base. Homo erectus is widest higher up giving it a distinctive pentagon shape. P.7 Homo erectus was around for over a million and a half years and so was a very successful species Homo sapiens is widest near the top of the skull. This is the parietal expansion. Doing this Lab You will prepare 2 graphs. Everyone should do their own graph and staple it to the short take home quiz due next week. You should work together in making the measurements and doing the graphs and any calculations. Corrections to the Lab Manual P. 4 The total of the numbers (about 1/3 of the way down the page) is 20 not 11. The sum of the squared deviations should be 20/ 5 = 4 not 11/5=2.2 The square root of 4 is 2. The C.V. at the bottom of the page should be 2/104 =.019 or 1.9% Corrections to the Lab Manual On P. 11 at # 3) cross out the words "as well as the male and female Homo sapiens" (Its about 1/3 of the way down the page). KNM-ER 1470 is about 2.4 million years old, not 1.9 mya (p.1) Lab Tips On P. 15 (for Station 5) the cranial volume for the specimens will be on a 3 x 5 index card. On P. 16 (for Station 6) the foramen magnum is hard to see on the Homo habilis plaster cast. It is more easily seen on the identical but better cast at Station 4. Reminders The Maxillary refers to the maxilla or the upper jaw. M2 refers to the second molar (the biggest teeth in the back). Bucco-lingual length (the cheek to tongue measurement of the molar). Terms to know The Index of Dimorphism (I.D.) is the mean (or average ) of the male divided by the mean (or average) of the female. Use a triangle symbol for the males. Use a circle for the males on your graphs. The Y axis runs vertically. The x axis runs horizontally. Gona, Ethiopia Stone tool flakes have been found at Gona Ethiopia from 2.6 mya Were they made by Homo habilis or by Paranthropines? They have not found the skeletons yet. Homo habilis and rudolphensis Brain size varies between 500 and 800 cc, overlapping the australopithecines at the low end and H. erectus. The average cranial capicity of H. habilis is about 40% larger than the average for A. africanus. Brain shape is more humanlike. Brain is reorganized! Early Genus Homo. The dividing line is based upon tool making, brain size and dentition. Homo rudolphensis (left) A. africanus (right) The Evolution of the Human Brain Not only is the brain size (cranial capacity) increasing but the architecture of the brain is changing and evolving. One of the defining characteristics of Homo sapiens is the use of grammar and language which is a left brain area in most people. Broca’s Area Broca’s area in the brain shows up in one Homo habilis endocast. This may be related to increased tool use (today the area is associated with making the movements of speech). Q: Did habilis have a gestural speech? The brain is evolving a different relative size for different areas. Brain architecture is changing as well as size. Homo habilis did not have just a larger version of an Australopithicine brain. Childbirth Changes in the pubis and pelvis occurred to allow a bigger birth canal and are are associated with encephalization (growth of the cranium), and they seem to have occurred at nearly the same time that encephalization did in Homo habilis. Homo habilis behavior Oldowan tools (from "Olduvai") are simple chopping "pebble" tools and the flakes may have been more important than the chopper. Useful for breaking into bone to get at marrow when scavenging (about 1500 calories) Bone marrow is like butter and using a modern soup bone to make soup uses the same principal. Oldowan Stone Tools The flakes can be used for cutting trough bone and muscles and leave "CUTMARKS" Cutmarks over animal teeth marks indicate the scavenger got there after the kill by a carnivore. Animal teeth over cutmarks indicate the animal was scavengeing and the human got there first Cutmarks Cutmarks on human bone do NOT necessarily mean "cannibalism." In Hawaii up until the last century people still defleshed their loved ones to protect the bones which were believed to have mana or sacred power. Bones were hidden in lava tubes so they could not be turned into e.g. fishooks to exploit the mana. Scavenging or hunting? H. habilis was probably a scavenger. Over half the cutmarks on bone are on bones with little meat e.g. lower legs suggesting habilis was taking what was left over from carnivores. There are no complete carcasses. Usually only the leftover parts are found. Cutmarks are often over the animal tooth marks. Scavenging Animals have a hard time breaking into bone. Marrow is rich in fat - walking food. Stone tools and the freed hands of bipedalism allowed habilis to get into the marrow after the lions, hyenas, vultures, etc. had picked the animal clean. (Food niche). Scavenging is intermittent food but is available year round unlike vegetation which is seasonal. Homo erectus a "deflated football shaped" cranium Pentagon shape to the back of the cranium. Shivel shaped incisors. Impressive brow ridges. Occipital angle. Homo erectus 2 million to 300,000 years ago. (there are claims that they lived in Java, Indonesia until 35,000 years ago. Like habilis, the face has protruding jaws with large molars, no chin, thick brow ridges, and a long low skull. Brain size varys between 750 and 1225 cc. Early erectus averages about 900 cc Late erectus averages about 1100 cc erectus sagittal keels (not crests) Some Asian erectus skulls have a sagittal keel (not crest). e.g. this Homo erectus from Java, Indonesia. Homo erectus Skeleton is more robust than those of modern humans (implying greater strength). Body proportions vary. (below) Homo erectus Sangiran, Indonesia Nariokotome Boy is tall and slender, like modern humans from the same area. aka "Turkana Boy" after Lake Turkana, Kenya 12 year old boy based on dental eruption dated to 1.6 mya. Would have been 6 feet tall in adulthood. H.erectus spread out of Africa Study of the Turkana Boy indicates erectus may have been more efficient at walking than modern humans, whose skeletons have had to adapt to allow for the birth of larger-brained infants (Willis 1989). Homo habilis and all the australopithecines are found only in Africa. Erectus is found through Africa and Asia (and was probably in Europe at Boxgrove). First use of fire Erectus probably used fire. South African dates are not as good as elsewhere due to the lack of volcanic ash deposits. Fire allows cooking, warmth, extends the day, provides protection from predators at night, and is a community focus at night. Acheulian Hand Axes. Stone tools are more sophisticated than those of habilis as of 1.4 mya. Acheulian Hand Axes are teardrop shaped bifaces (worked or sharpened on both sides and all the way around the tool). Useful for butchering, scraping, and breaking bones. Possibly a core for flakes, a weapon, a digging tool, axe, etc. a"Swiss Army Knife" Homo erectus was a hunter Olduvai Gorge 1.5 mya shows all the bones of the animal at butchering sites (not scavenged parts). All of the carcass is used. Increased variety of stone tools using a mental template or pattern (They are fairly consistent over a million years of manufacture). Animal toothmarks are over the cutmarks. Homo erectus aka "Peking man" The few limb bones found of Peking Man indicate a shorter, sturdier build. Zhokoudian cave in China showed Homo erectus used fire and hunted deer, wild pigs, and water buffalo. The tools in China were chopper tools not Acheulian Hand Axes. The "bamboo line" - bamboo may have been used instead.
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