The Descent of Man

Supplemental Lecture (97/05/04 update) by Stephen T. Abedon

  1. Chapter title: Descent of Man
    1. A list of vocabulary words is found toward the end of this document
    2. "Homo sapiens did not appear on the earth, just a geologic second ago, because evolutionary theory predicts such an outcome based on themes of progress and increasing neural complexity. Humans arose, rather, as a fortuitous and contingent outcome of thousands of linked events, any one of which could have occurred differently and sent history on an alternative pathway that would not have led to consciousness. To cite just four among a multitude:
      1. If our inconspicuous and fragile lineage had not been among the few survivors of the initial radiation of multicellular animal life in the Cambrian explosion 530 million years ago, then no vertebrates would have inhabited the earth at all.
      2. If a small and unpromising group of lobe-finned fishes had not evolved fin bones with a strong central axis capable of bearing weight on land, then vertebrates might never have become terrestrial.
      3. If a large extraterrestrial body had not struck the earth 65 million years ago, then dinosaurs would still be dominant and mammals insignificant (the situation that had prevailed for 100 million years previously).
      4. If a small lineage of primates had not evolved upright posture for the drying African savannas just two to four million years ago, then our ancestry might have ended in a line of apes that, like the chimpanzee and gorilla today, would have become ecologically marginal and probably doomed to extinction despite their remarkable behavioral complexity. . .
    3. Our conventional desire to view history as progressive, and to see humans as predictably dominant, has grossly distorted our interpretation of life's pathway by falsely placing in the center of things a relatively minor phenomenon (humans) that arises only as a side consequence." (Gould, 1994).
    4. In this lecture we will trace the evolution of humanity beginning with the origin of primates through the comings and goings of Genus Homo.
  2. Lecture Review
    1. Below is a trace through time of the origin of humans including various key events. Time is in units of millions of years before present. Note that these dates are approximations at best. The only consistent thing I can say about the various dates for various events is that those supplied by various authors are not consistent. For example, one author places the tree shrew-like progenitor of primates as appearing 55 million years ago rather than the 80 million years ago indicated below. Thus, other than the various items listed as occurring 65 million years ago (as well established a date as any), don't assume that the absolute dates (or even approximations) are cast in easily dated stone. However, relative dates often are on much firmer ground. In other words, should you decide to recall the year that orangutans diverged from the rest of Hominoidea, think of it as about eight million years ago assuming that gibbons diverged about 10 million years ago, etc. Such is the nature of our understanding of the deep past.

    millions of years
    before present



    origin of earth


    appearance of mammals


    appearance of dinosaurs


    appearance of birds


    appearance of tree shrew-like primate progenitor


    meteor strikes earth leading to extinction of dinosaurs


    end of the Cretaceous period


    beginning of the Tertiary period


    beginning of the "age of mammals"


    appearance of primates


    appearance of monkeys


    appearance of apes


    appearance of gibbons as separate lineage


    appearance of orangutans as separate lineage


    appearance of gorillas as separate lineage


    appearance of chimpanzees as separate lineage


    appearance of hominids


    appearance of Australopithecus afarensis


    appearance of bipedalism


    genus Homo and genus Australopithecus diverge


    appearance of Homo habilis


    appearance of Homo erectus


    control of fire


    the last of the australopithecines goes extinct


    appearance of Homo sapiens


    appearance of anatomically modern Homo sapiens


    burial of the dead


    appearance of drawing and protowriting


    appearance of civilization


    appearance of writing


    Magna Charta


    declaration of independence


    space travel (and The Beatles!)


    hand-held calculators


    personal computers


    world wide web


  3. Tree shrews

    1. Tree shrews are:
      1. small
      2. arboreal
      3. insectivorous
      4. mammals
    2. Tree shrews are either descended with little modification from the primate progenitor, or are thought to at least resemble morphologically and behaviorally the primate progenitor.
  4. Primates
    1. Characteristics:
      1. Primates are a group of mammals which:
        1. are mostly arboreal
        2. have grasping fingers instead of claws
        3. have binocular vision*
      2. *Binocular vision means having eyes placed in the front of heads with overlapping fields of vision. This arrangement allows the brain to interpret the visual world much more efficiently as three dimensional space.
    2. Diet driven evolution:
      1. Primates began as insect eaters.
      2. With time, however, primates came to rely on diets based to a large extent on the vegetation found in the canopies of trees.
      3. "Selective pressures . . . favored considerable enhancement of the visual apparatus (including depth perception, sharpened acuity and color vision), thereby helping primates travel rapidly through the three-dimensional space of the forest canopy and easily discern the presence of ripe fruits or tiny, young leaves. And such pressures favored increased behavioral flexibility as well as the ability to learn and remember the identity and locations of edible plant parts. Foraging benefits conferred by the enhancement of visual and cognitive skills, in turn, promoted development of an unusually large brain, a characteristic of primates since their inception. . . As a group . . . primates have depended most strongly on selective feeding and on having the brain size, and thus the wit, to carry off this strategy. Other plant-eating orders, in contrast, have tended to focus heavily on morphological adaptations. . . Primates typically have larger brains than do other mammals of their size. (The author) believes the difference arose because primates feed very selectively, favoring the highest-quality plant parts." (p. 86, 89, 90, Milton, 1993)
  5. Monkeys
    1. Monkeys are a group of primates which:
      1. are diurnal*
      2. have color vision
      3. have opposable thumbs
      4. have expanded brains
      5. have extended child development
      6. have complex social structures
    2. *Active during the daytime as opposed to at night (nocturnal).
    3. African origin:
      1. The monkeys lineage originated in Africa.
      2. Today two distinct groups of monkeys exist:
        1. those which remain in Africa or have spread to Asia
        2. those which live in the Americas
      3. These geographically (and morphologically and phylogenetically) defined types are respectively referred to as:
        1. old world monkeys
        2. new world monkeys
  6. Apes [Hominoidea]
    1. Apes are (essentially) are monkeys with:
      1. large bodies
      2. large brains (relative to body size)
      3. no tails
    2. The extant apes (i.e., superfamily Hominoidea) include:
      1. gibbons
      2. gorillas
      3. orangutans
      4. chimpanzees
      5. humans
  7. Great apes
    1. The extant great apes include:
      1. gorillas
      2. orangutans
      3. chimpanzees
    2. This taxon, of course, is paraphyletic if humans are not included.
    3. Pongidae is a now largely discredited grouping of the great apes separately from that of human lineage.
    4. Paraphyletic taxon:
      1. Based on anatomic considerations alone, the grouping Pongidae was once considered to be monophyletic.
      2. Recent molecular data strongly argue that instead it is paraphyletic. That is, humans are more closely related to both chimpanzees and gorillas than any are to orangutans (i.e., the last common ancestor of humans, chimpanzees, and gorillas for a few million years coexisted with and was not identical to the ancestral orangutan).
      3. Note that even a grouping of chimpanzees and gorillas would now be considered paraphyletic since humans and chimpanzees are considered to be more closely related than chimpanzees and gorillas.
    5. Inconsistent usage:
      1. Note that the introductory biology text by Postlethwait & Hopson (1995) places humans in Pongidae while Raven & Johnson (1996) instead use Hominidae.
      2. Here we will employ Hominidae to describe the apes and consider Pongidae to be a subset of Hominidae, and one which is a valid clade only so long as humans are considered also to be members of Pongidae.
  8. Gibbons
    1. The gibbons are the first group that has managed to survive until modern times which branched away from the main trunk of Hominoidea.
    2. The gibbons thus are the most distant relatives of humans (or the other great apes) with superfamily Hominoidea.
  9. Orangutans
    1. Least related of great apes:
      1. The orangutan and the rest of Hominoidea last shared an ancestor prior to the divergence of gorillas, chimpanzees, and hominids from each other.
      2. That is, at the time of divergence of the orangutan, Hominoidea consisted of three distinct and one less distinct group:
        1. those direct ancestors of orangutan
        2. the various ancestral gibbons and gibbon-like lineages
        3. the single common gorilla, chimpanzee, hominid ancestor
        4. all the various other lineages that became extinct prior to modern times.
    2. In particular, "At the molecular level, gorilla, chimpanzee, and human beings are more closely related to one another than is any one of these to the Asian great ape, the orangutan." (p. 144, Tobias, 1992)
  10. Gorillas
    1. The gorillas are probably less closely related chimpanzees than hominids are to chimpanzees.
    2. This means that the gorilla ancestor and the common ancestor of hominids and chimpanzees coexisted, by definition, prior to the divergence of the hominids and the chimpanzees from each other.
  11. Chimpanzees
    1. Closest relatives:
      1. The most closely related living organisms to humans are the chimpanzees.
      2. This is especially true for chimpanzees species known as bonobos, or pigmy chimpanzees.
    2. The sequence of the human genome and that of the chimpanzee differs little more than 1%.
  12. Hominid [Hominidae]
    1. Bipedal apes:
      1. Members of family Hominidae include all of the upright walking (bipedal) apes, extant and extinct.
      2. Note that the oldest members of family Hominidae is considered to have diverged from the common human-chimpanzee ancestor. Consequently, family Hominidae can simultaneously be considered to be monophyletic and to exclude all of the chimpanzees.
    2. Uncertainty:
      1. The timing of the divergence between family Hominidae and chimpanzees is best estimated from molecular data.
      2. Unfortunately, from molecular data it is difficult to infer morphological (much less behavioral) information.
      3. This, combined with a fragmentary fossil record from the time of this split results in investigators having little knowledge of the appearance of the human (and chimpanzee) ancestors immediately prior to and following their divergence.
      4. That is, it is thought the first members post-divergence from the chimpanzee lineage were likely not bipedal (with bipedalism developing only later), though we don't yet the have strong evidence that this actually is true.
    3. What we do know is that, minimally (and ultimately), hominids came to consist of two evolutionary branches, one consisting of genus Homo and the other consisting genus Australopithecus.
  13. Bipedalism
    1. Since we know little about the last common ancestor of humans and chimpanzees, as well as the immediately post-common ancestor of humans, we cannot say with reasonable conviction that the earliest, post-common chimpanzee linaege ancestors of family Hominidae walked upright, though clearly this was a prominent feature in future hominid evolution.
    2. Evolution from chimp-like morphology:
      1. Given the relative lack of divergence of chimpanzees from gorillas, compared with that exhibited by humans, it is more probable that the last common ancestor to both humans and chimpanzees looked and acted more like a chimpanzee than like a human.
      2. "The spread of lighter woodland and savannah, and the retreat of the margins of the primeval forests, could well have created conditions in which the tendency toward an erect posture and bipedalism was favored. The ability to run across the high grass cover of the savannah, perhaps from one woodland stream to another, might have held advantages for those apes that could 'walk tall,' since uprightness would have enabled its possessors to see over the high grass and to watch out for predators like lions and saber-toothed big cats." (p. 149, Tobias, 1992)
  14. Small brain beginning
    1. Bipedalism predated large brains:
      1. The first members of family Hominidae appear not to have had relatively large brains (i.e., relative to that of chimpanzees).
      2. Particularly, there is strong fossil evidence that later members of family Hominidae simultaneously possessed both bipedalism and small brains (i.e., chimpanzee size).
      3. Since chimpanzees do not walk upright (and, indeed, employ a method of locomotion similar to that employed by gorillas), in all likelihood the earliest, non-chimpanzee lineage, common ancestor of Hominidae neither walked upright nor had a large brain.
  15. East side story
    1. Eastern African origins:
      1. The origin of family Hominidae is routinely considered to be traceable to Eastern Africa.
      2. Prior to the chimpanzee-Hominid split, all of the range of our common ancestors probably covered of much of Africa.
      3. However, as we have learned, speciation likely occurs in small, geographically isolated groups. And, at the dawn of the evolution of Hominidae as a separate lineage from chimpanzee, Hominidae is found in East Africa, but chimpanzee is not.
    2. Rift valley
      1. There exists a prominent geographical feature that separates the ranges of the early humans and extant chimpanzees.
      2. It is called the Rift Valley and it constitutes a long North-South valley that separates East Africa from Central Africa (it is, to those who appreciate plate tectonics, a proto-ocean forming as the East African plate pulls away from central Africa).
      3. Thus, on the west side of the Rift Valley (as it began to form as a significant geographical barrier and as the chimpanzee-Hominid split occurred) was found the chimpanzee ancestor living in a forested environment that was similar to that in which the chimpanzee-Hominid last common ancestor also had lived.
    3. East side drying
      1. On the eastern side of the Rift Valley environmental change occurred which included a general drying trend.
      2. This drying converted what was once forest into open savanna.
      3. The dawn of Hominidae thus is thought to have coincided with both the opening of the Rift Valley and an associated drying across the Hominidae range, i.e., environmental change combined with geographical isolation.
      4. By this reckoning, Hominidae diverged morphological from chimpanzee at first and at least in part in the course of adaptation to a new, drier environment.
  16. Australopithecus afarensis
    1. Early hominid with very complete skeleton:
      1. Australopithecus afarensis is an early species of family Hominidae.
      2. It is a particularly important species both due to its age and because we possess reasonably complete skeletons.
      3. One member of A. afarensis, in fact, is the famous "Lucy" discovered by Donald Johanson in 1974.
    2. Lucy, and other, later australopithecines, was bipedal but small brained indicating that upright walking and a large brain did not evolve hand in hand.
  17. Other australopithecines
    1. Various post-Lucy species:
      1. Various post-A. afarensis commonly accepted Australopithecus species include:
        1. A. africanus
        2. A. boisei
        3. A. robustus
      2. Note that A. robustus was a sympatric (lived side by side) contemporary of genus Homo, but which possessed a jaw and teeth that were highly adapted to a rough and abrasive diet.
      3. In fact, australopithecines in various forms survived long after genus Homo was up and running. The last australopithecines walked the earth approximately a million years ago.
    2. All small-brained bipedals:
      1. All species of genus Australopithecus are thought to have had relatively small brain sizes (i.e., to body size), somewhere between that seen with modern gorillas and modern chimpanzees.
      2. Thus, no australopithecine would be considered large brained in a genus Homo sense.
      3. They also all appear to have been upright walkers.
      4. Think about it, a mere 1 million years ago small brained, bipedal hominids still walked the earth.
    3. Australopithecines are not considered to be members of genus Homo though they were hominids, and though genus Homo appears to have evolved from genus Australopithecus (which, of course, makes genus Australopithecus paraphyletic).
  18. Man the scavenger
    1. Switch back to meat:
      1. The evolution of genus Homo is thought to have been influenced to a significant extent by the practice of basing a greater portion the diet on the ingestion of meat than that obtained by either the great apes or members of genus Australopithecus. Thus, we are Homo the meat eaters.
      2. However, were our ancestors who began this practice also the hunters of the meat they began to consume in increasing amounts?
      3. In fact, there is a high likelihood that concepts of man the hunter are simply another example of man the arrogant.
      4. Instead, it is more likely that early Homo obtained their meat by stealing it from those much more adept at killing (leopards, for example). That is, evidence that early Homo hunted is not nearly as robust as evidence that early Homo scavenged.
    2. Scenario:
      1. One interpretation of the evidence goes like this:
        1. Early Homo was omnivorous (eaters of both vegetables and meat) and living in riparian habitats (rivers, which provided trees for refuge from predators).
        2. There they gathered plants which constituted the core of the early Homo diet.
        3. Especially during times of few (dry season, for example) scavenging took on particular importance.
        4. One source of meat was the bone marrow of large kills (brought down by lions and saber toothed tigers), a source of meat available only to them and the hyenas. Also potentially available were leopard kills, the scavenging (actually stealing) of which was a role early Homo alone may have filled.
      2. "The earliest hominids probably scavenged and took small prey with their hands, as chimpanzees and baboons do. Only their next step was unique: they began to use tools to butcher large carcasses that nonhuman primates cannot exploit. The difficulty of this leap (to the use of tools to butcher) belies the charge that scavenging offers no challenge that might select for human qualities. . . Scavenging is not at all easy for a slow, small, dull-toothed primate. To locate scavengeable carcasses before others did, we had to learn how to interpret the diverse cues to the presence of a carcass in riparian woodlands. They include the labored, low-level, early-morning, beeline flight of a single vulture toward a kill; vultures perched in mid-canopy rather than at the crown of a tree, where they nest; appendages of a concealed leopard or of its kill dangling from a branch; and tufts of ungulate hair or fresh claw marks at the base of a leopards favorite feeding tree. At night, the loud 'laughing' of hyenas at a fresh kill, the panicked braying of a zebra being attacked, the grunting of a frightened wildebeest---all serve notice of where to find an abandoned carcass when morning comes." (p. 94-95, Blumenschine and Cavallo, 1992)
    3. Scavenging, brains, and hunting:
      1. The bigger the primate brain, the more complex, varied, extensive, and higher quality is the food supply potentially available to the possessing organism.
      2. Having access to a high quality food supply supplies two things:
        1. it allows the support of a big brain, which, gram for gram, is the most metabolically expensive tissue animals have
        2. it maintains the species as generalists and therefore potentially adaptable to new situations and environmental conditions
      3. Genus Homo thus apparently expanded the primate tendency toward exploit generalized food supplies by focusing it additionally toward the difficult art of scavenging meat.
      4. This may have in turn driven the evolution of an even larger brain which ultimately set the stage for the later development of man the hunter.
      5. Hunting, of course, is an even more difficult strategy for obtaining a varied diet, which in turn may have supplied one component of the further selection pressure necessary to drive additional brain expansion.
  19. Homo habilis
    1. Big brained bipedal apes:
      1. Genus Homo combined strikingly large brains with the bipedalism of the australopithecines.
      2. The reason for the development of larger brains likely has an ecological explanation (see man the scavenger, above, for one possibility or aspect).
    2. Early genus Homo:
      1. The first relatively well accepted member of genus Homo is Homo habilis, handy man.
      2. Compared with Australopithecus africanus, H. habilis more resembled with respect to:
        1. brain size
        2. brain form
        3. teeth size
        4. teeth form
      3. Perhaps of greatest significance, however, was H. habilis's significantly increased reliance on the use of tools for eating and survival.
      4. "H. habilis was nearer to modern humans than A. africanus is with respect to size and form of the brain, size and morphology of the teeth, and the adjustment to an erect posture, as well as in many other features. . . (also) H. habilis, it seems, became obligate stone toolmakers and users, whereas the late robust and hyper-robust australopithecines might have been only facultative toolmakers and users (able to make and use stone tools, but equally able to survive without them). . . The robust and hyper-robust australopithecines (may have) prepared their food predominantly in their mouths, chewing it between their greatly expanded upper and lower cheek teeth, whereas H. habilis prepared its food with hand-held stone tools prior to eating." (p. 158, 159 Tobias, 1992)
  20. Homo erectus
    1. Most successful Homo species:
      1. Humanity had truly almost arrived as H. erectus replaced H. habilis as the dominant Homo species (resulting in the extinction of H. habilis).
      2. H. erectus, in terms of time spent on the earth, was the most successful of Homo species. She:
        1. lived in large groups
        2. controlled fire
        3. had a much more sophisticated "tool kit" than all animals that came before her
        4. spread her kind throughout the old world
      3. She was also the most culturally advanced creature of any previous.
  21. Homo sapiens
    1. H. erectus was replaced by an archaic form of H. sapiens.
  22. Anatomically modern Homo sapiens
    1. 100,000 years of anatomical moderness:
      1. Anatomically modern H. sapiens began replacing the various archaic forms approximately 100,000 years ago.
      2. All of humanity is descended from these anatomically modern H. sapiens.
    2. Cultural evolution:
      1. Anatomically modern H. sapiens have the duel distinction of:
        1. having raised cultural evolution, the practice of passing non-genetic information from parent to child, to higher levels than any other animal could dream of
        2. of using that skill to drive (largely not only without abatement but to an increasing extent) her entire home planet to the brink of ecological/environmental collapse.
      2. Clearly humans have become very good at what we do. Perhaps we have gotten a little too good?
    3. Man's future:
      1. This is not a course on anthropology so we will not consider humanity's achievements beyond this except as they pertain to biological sciences.
      2. We will also avoid speculating on mankind's biological future except to leave you pondering these important considerations:
        1. Only with a knowledge of evolutionary biology can one successfully subvert evolution.
        2. The one indisputable rule of evolution is that all species go extinct.
        3. Profound extinction of lineages usually occurs as a consequence of failure to adapt to changing environments (especially when those changes are abrupt).
        4. Consistently, seemingly omnipotent human civilizations of the past have had a nasty tendency of collapsing due to self inflicted (or perpetuated) environmental change. Indeed, our entire world-wide civilization is just as dependent as it ever has been on the existence of a few inches of top soil and the fact that more often than not the rains come at appropriate times.
        5. Modern man, at an unprecedented rate, is changing her environment for the worst. Are you prepared to survive a changing environment? Are any of us? Could you survive even a month in the absence of a local food market and a few gallons of gasoline refined from oil mined half-way around the world? In a world of so many, could any of us?
  23. Mankind
    1. Less strictly, mankind may be defined as members of family Hominidae.
    2. More strictly, the term mankind may be applied to members of genus Homo.
    3. Most strictly, the use of the term mankind may be limited to extant members of genus Homo.
  24. Ancestors
    1. When is one not one?
      1. The lay public and even scientists tend to use the term ancestor in a very fast and loose manner when describing exciting fossils. Strictly, an ancestor is an individual which you and or I can trace an unbroken blood line back to. Thus, our great-grandparents, unless we were adopted, were our ancestors.
      2. All of humanity can trace their ancestry back to common individuals. The last common ancestor of all of humanity was in all likelihood also human. However, if one finds an ancient human fossil, does that imply that that person is an ancestor to all of humanity? Not necessarily (and, in fact, not likely). However, we might still describe that individual as an ancestor to humanity because she was of the proper species and lived at approximately the same time as we expect of our true common ancestor.
      3. As we go farther back in time, things start to become not only more and more vague as to what exactly a true ancestor must have looked like, but even what species a true ancestor must have been (or morphology must have had). Thus, if you think of evolution has producing a bush of diverging lineages, a true ancestor is found on a branch that is directly between you and the center of the bush. Everything else is not an ancestor in the strictest sense.
      4. However, a separate species that was closely related to the true ancestor might still be referred to as an ancestor. That is, with only a slight divergence from the true lineage, combined with ultimate extinction (since divergence from the chimpanzee ancestor, all members on our branch but one have gone extinct) leaves it very difficult to say, even down to the level of the species, whether a given individual or group is in reality an ancestor (though its easier to argue that a particularly divergent lineage is not). However, at this point operationally it really stops making all that much of a difference. Thus, an Australopithecus afarensis-like species was probably a direct human ancestor, though A. afarensis itself may not have been that ancestor, and, with high probability, any individual fossil probably really isn't a true, direct ancestor either.
  25. Last common ancestor
    1. A last common ancestor basically the often hypothetical organism which was the last species to exist prior to the divergence of that species into the two or more distinct species being compared. Since, as noted above, it is often very difficult to assign clear ancestral status to a fossil, the last common ancestor is often not associated with any given fossil with high certainty. Nevertheless, for any two divergent lines, some last common ancestor must have existed at some time in the past (assuming the existence of some universal ancestor). Often through methods of molecular evolution the time of the divergence and therefore that date at which the last common ancestor lived can be estimated with reasonable precision.
  26. Universal ancestor
    1. The universal ancestor is the last common ancestor of all living things on planet Earth.
  27. Earliest common ancestor
    1. Earliest common ancestor is probably a term I've coined here. I use it to describe the first species of a lineage. That is, the base of the tree---the root of the clade. Thus, the earliest common ancestor of Hominidae is the first species in the Hominid lineage following divergence from the chimpanzee lineage (i.e., the first species post-last common ancestor). The earliest common ancestor is the root species of a monophyletic tree.
  28. Culture
    1. Culture is information which is passed on from parent to offspring (more generally, from the older to the younger) through non-genetic means. For example, the ability to make stone tools or speak a specific language. Or, in less anthrocentric terms, the ability to hunt or make a den, etc.
  29. Cultural evolution
    1. Cultural evolution is change in culture over time. Cultural evolution can be very powerful to an intelligent generalist because the means by which variation occurs often is directed (one tries some new thing that one hopes will work) and the rate at which failed experiments may be culled is often very rapid, while simultaneously not necessarily leading to the extinction of the carrier of the variant. Thus, cultural evolution occurs by a series of accidental or purposeful trials, errors, and culling, and may be transmitted between individuals lacking a close blood relation.
  30. Vocabulary
    1. Anatomically modern Homo sapiens
    2. Ancestors (when is one not one?)
    3. Apes
    4. Australopithecines (other)
    5. Australopithecus afarensis
    6. Bipedalism
    7. Chimpanzee
    8. Cultural evolution
    9. Culture
    10. Earliest common ancestor
    11. East side story
    12. Great apes
    13. Gibbons
    14. Gorillas
    15. Hominid
    16. Hominidae
    17. Hominoid
    18. Hominoidea
    19. Homo erectus
    20. Homo habilis
    21. Homo sapiens
    22. Last common ancestor
    23. Man the scavenger
    24. Mankind
    25. Monkeys
    26. Orangutans
    27. Pongidae
    28. Primates
    29. Tree shrew
    30. Universal ancestor
  31. Practice questions
    1. Which first controlled fire?
      1. Australopithecus afarensis
      2. Australopithecus boisei
      3. Australopithecus africanus
      4. Australopithecus robustus
      5. Homo habilis
      6. Homo erectus
      7. Homo sapiens archaic
    2. What's the difference between a hominid and a hominoid?
    3. What description best describes the phylogenetic grouping consisting of (i) the gorillas, the chimpanzees, humans, and the gibbons; (ii) all of the ancestors of these extant animals going back to their last common ancestor; and (iii) all of the extinct lineages stemming from this last common ancestral species? (circle best answer)
      1. Pongidae
      2. a monophyletic grouping
      3. Hominoidea
      4. a paraphyletic grouping
      5. all of the above
      6. none of the above
    4. According to the hypothesis concerning the Rift Valley, where did Hominids diverge from the chimpanzee-human most recent common ancestor?
    5. According to the "man the scavenger" hypothesis, selection for large brains (i.e., greater than those of the chimpanzee) initially occurred within the context of a broadening of the hominid diet to include scavenged meat. If so, which of the following either scavenged, or evolved in the course of scavenging for meat?
      1. Australopithecus afarensis
      2. Australopithecus boisei
      3. Australopithecus africanus
      4. Australopithecus robustus
      5. Homo habilis
      6. Homo erectus
      7. Homo sapiens archaic
    6. Of extant apes, with which do humans show the greatest evolutionary divergence?
  32. Practice question answers
    1. vi, Homo erectus
    2. A hominid is a monophyletic subset of the hominoids, one whose members exhibited, among other things, a bipedal gate. The hominoids is a monophyletic clade consisting of all of the apes and the hominids.
    3. iv, a paraphyletic grouping. That is, orangutans are missing from the grouping.
    4. East Africa
    5. v, Homo habilis
    6. gibbons
  33. References
    1. Blumenschine, R.J., Cavallo, J.A. (1992). Scavenging and human evolution. Scientific American October:90-96.
    2. Coppens, Y. (1994). East side story: The origin of humankind. Scientific American May:88-95.
    3. Milton, K. (1993). Diet and primate evolution. Scientific American August:86-93.
    4. Postlethwaite, J.H., Hopson, J.L. (1995). The Nature of Life. Third Edition. McGraw-Hill, Inc., New York. pp. 433-444.
    5. Raven, P.H., Johnson, G.B. (1995). Biology (updated version). Third Edition. Wm. C. Brown publishers, Dubuque, Iowa. pp. 440-448.
    6. Raven, P. H., Johnson, G. B. (1996). Biology. Fourth Edition. Wm. C. Brown publishers, Dubuque, Iowa. pp. 515-530, 637.
    7. Tobias, P.V. (1992). Major events in the history of mankind. Major Events in the History of Life. J. W. Schopf (ed.). Jones and Bartlett Publishers, Boston. pp. 141-175.


Reprinted with the kind permission of Stephen T. Abedon
Education 2000 -