Anthropology Chapter 8

Looking at this entire array of Eocene fossils, it's certain that they were

(1) primates; (2) widely distributed; and (3) mostly extinct by the end of the Eocene (around 33 mya)

Bipedal in relation to tool carrying abilities

. These earliest members of the hominin lineage, who lived prior to 5 mya, may have carried objects such as naturally sharp stones or stone flakes, parts of carcasses, and pieces of wood. Also, as you'll see later in this chapter, by 6 mya—and perhaps as early as 7 mya— hominins had developed one crucial advantage: They were bipedal and so could more easily carry all kinds of objects from place to place. Ultimately, the efficient exploitation of widely distributed resources would probably have led to using "central" spots where the most important implements—especially stone objects—were cached, or collected (Potts, 1991).

. Our primary focus will be to organize them by time and by major evolutionary trends. In so doing, we recognize three major groups

1. Pre-australopiths -the earliest and most primitive (possible) hominins (6+-4.4 mya) 2. Australopiths—diverse forms, some more primitive, others highly derived (4.2-1.2 mya) 3. Early Homo—the first members of our genus(2+-1.4mya)

From the time that fossil sites are first located until the eventual interpretation of hominin evolutionary patterns, several steps take place. Ideally, they should follow a logical order, for if interpretations are made too hastily, they confuse important issues for many years. Here's a reasonable sequence

1. Selecting and surveying sites 2. Excavating sites and recovering fossil hominins 3. Designating individual finds with specimen numbers for clear reference 4. Cleaning, preparing, studying, and describing fossils 5. Comparing with other fossil material—in achronological framework if possible 6. Comparing fossil variation with known ranges of variation in closely related groups of living primates and analyzing ancestral and derived characteristics 7. Assigning taxonomic names to fossil material 8. Publishing results and interpretations in peer-review

Conclusions drawn from Miocene hominoids

1. These are hominoids—more closely related to the ape-human lineage than to Old World monkeys. 2. They are mostly large-bodied hominoids, that is, more connected to the lineages of orangutans, gorillas, chimpanzees, and humans than to smaller-bodied apes (for example, gibbons and siamangs). 3. Most of the Miocene species thus far discovered are so derived that they are probably not ancestral to any living form. 4. One lineage that appears well established is Sivapithecus from Turkey and Pakistan. Sivapithecus shows some highly derived facial features similar to the modern orangutan, suggesting a fairly close evolutionary connection . 5. Evidence of definite hominins from the Miocene hasn't yet been indisputably confirmed. However, exciting recent finds from Kenya, Ethiopia, and Chad (the latter dating as far back as 7-6 mya) suggest that hominins diverged sometime

Given the 3-million-year time range as well as quite varied ecological niches. first let's emphasize the major features that all australopiths share

1. They are all clearly bipedal (although not necessarily identical to Homoin in this regard). 2. They all have relatively small brains(at least compared with Homo) 3. They all have large teeth, particularly the back teeth, with thick to very thick enamel on the molar

Four general points are certain concerning Miocene hominoid fossils:

1. They are widespread geographically; 2. they are numerous; 3. they span essentially the entirety of the Miocene, with known remains dated between 23 and 6 mya; and at present, 4. they are poorly understood.

Ardi

2009, Tim White and colleagues published their truly remarkable finds. By far, the most informative fossil is the partial skeleton. Even though it was found crushed and fragmented into hundreds of small pieces, years of work and computer imaging have now allowed researchers to interpret this 4.4-million-year-old individual. The skeleton, nicknamed "Ardi," has more than 50 percent of the skeleton represented; however, because it was found in such poor condition, any reconstruction must be seen as provisional and open to varying interpretations. Ardi has been sexed as female and contains several key portions, including a skull, a pelvis, and almost complete hands and feet Brain size, estimated between 300 and 350 cm3, is quite small, being no larger than a chimpanzee. Height is estimated at close to 4 feet, with a body weight of around 110 pounds. Compared with other early hominins, such a body size would be similar to that of a male and well above average for a female. According to Tim White and colleagues, both areas of the body show key anatomical changes indicating that Ardipithecus was a competent biped. For example, the ilium is short and broad , and the foot has been modified to act as a prop for propulsion during walking. However, Ardi also contains some big surprises. Although the shape of the ilium seems to show bipedal abilities, other parts of the pelvis show more ancestral ("primitive") hominoid characteristics. One thing that everyone agrees on is that Ardi was an able climber who likely was well adapted to walking on all fours along the tops of branches. It seems clear that she spent a lot of time in the trees

Sahelanthropus tchadensis

7-6 mya In recognition of this unique combination of characteristics, paleoanthropologists have placed the Toros-Menalla remains into a new genus and species of hominin, Sahelanthropus tchadensis (Sahel being the region of the southern Sahara Desert in North Africa) difficult to see how Sahelanthropus could be anything but a hominin. However, the position of its foramen magnum is intermediate between that of a quadrupedal ape and that of a bipedal hominin, making it unclear if its skull would have been balanced over a bipedal spinal column. some researchers (Wolpoff et al., 2002) suggest that at this time, "ape" may be a better classification for Sahelanthropus

Scientists use two basic types of dating for to place artifact in chronological order

: relative dating and chronometric dating (also known as absolute dating).

australopiths

A colloquial name referring to a diverse group of Plio-Pleistocene African hominins. Australopiths are the most abundant and widely distributed of all early hominins and are also the most completely studied.

Apidium

A parapithecid genus from the Oligocene, possibly ancestral to anthropoids. Apidium is represented by several dozen jaws or partial dentitions as well as many postcranial remain Owing to its primitive dental arrangement, some paleontologists have suggested that Apidium may lie near or even before the evolutionary divergence of Old and New World anthropoids. It's thought that this squirrel-sized primate ate mostly fruits and some seeds and was most likely an arboreal quadruped, adept at leaping and springing.

mosaic evolution

A pattern of evolution in which the rate of evolution in one functional system varies from that in other systems. For example, in hominin evolution, the dental system, locomotor system, and neurological system (especially the brain) all evolved at markedly different rate

sagittal crest

A ridge of bone that runs down the middle of the cranium like a short Mohawk. this serves as the attachment for the large temporal muscles, indicating strong chewing.

Fayum

A site southwest of Cairo, Egypt, where the world's best record of Oligocene primate fossils has been found. .

another well known chronometric technique

A well-known and commonly used chronometric technique involves carbon-14 (14C), with a half-life of 5,730 years. This method is used to date organic material (such as wood, charcoal, and plant fibers) as recent as a few hundred years old and can be extended as far back as 75,000 years, although the probability of error rises rapidly after 40,000 years. The physical basis of this technique is also radiometric; that is, it's tied to the measurement of radioactive decay of an isotope (14C) into another, more stable form. Radiocarbon dating has proved especially relevant for calibrating the latter stages of human evolution, including the Neandertals and the appearance of modern Homo sapiens

How tall is Lucy?

A. afarensis was a short hominin. From her partial skeleton, Lucy is estimated to be only 3 to 4 feet tall. A. afarensis was quite sexually dimorphic: The larger individuals are male, and the smaller ones, such as Lucy, are female.

obligate biped

Adapted for walking only on two legs, with no ability to walk on four

The important genuses from the Fayum

Aegyptopithecus & Apidium

human culture

Another point to remember is that human culture, at least as it's defined in contemporary contexts, involves much more than toolmaking capacity. For humans, culture integrates an entire adaptive strategy involving cognitive, political, social, and economic components.

biocultural evolution

As cognitive abilities developed, more efficient means of communication and learning resulted. Largely because of consequent neurological reorganization, more elaborate tools and social relationships also emerged. These, in turn, selected for greater intelligence, which in turn selected for further neural elaboration. Quite clearly, these mutual dynamic interactions are at the very heart of what we call hominin biocultural evolution.

Australopithecus sediba (sediba means "wellspring" or "fountain" in the local language)

Australopith-like characteristics seen in A. sediba include a small brain (estimated at 420 cm3), long arms with curved fingers, and several primitive traits in the feet. In these respects A. sediba most resembles its potential immediate South African predecessor, A. africanus. The analysis of the lower limb anatomy suggests that A. sediba would have swayed side to side while walking, an unusual form of bipedal locomotion (DeSilva et al., 2013)

why is the Laetoli are hard to date?

Because the Laetoli area was covered periodically by ash falls from nearby volcanic eruptions, accurate dating is possible and has provided dates of 3.7-3.5 mya. Dating from the Hadar region isn't as straightforward, but more complete dating calibration using a variety of techniques has determined a range of 3.9-3 mya for the hominin discoveries from this area.

Australopithecus anamensis

Because these particular fossils have initially been interpreted as more primitive than all the later members of the genus Australopithecus, paleoanthropologists have provisionally assigned them to a separate species. This important fossil species is now called Australopithecus anamensis, and some researchers suggest that it is a potential ancestor for many later australopiths as well as perhaps early members of the genus Homo

Homo habilis

Better-preserved evidence of a Plio-Pleistocene hominin with a significantly larger brain than seen in australopiths was first suggested by Louis Leakey in the early 1960s on the basis of fragmentary remains found at Olduvai Gorge in Tanzania. Leakey and his colleagues gave a new species designation to these fossil remains, naming them Homo habilis. There may, in fact, have been more than one species of Homo living in Africa during the Plio-Pleistocene. So, more generally, we'll refer to them all as "early Homo"; the species Homo habilis refers particularly to those early Homo fossils from Olduvai and the Turkana Basin. The naming of this fossil material as Homo habilis ("handy man") was meaningful from two perspectives. First of all, Leakey argued that members of this group were the early Olduvai toolmakers. Second, and most significantly, by calling this group Homo, Leakey was arguing for at least two separate branches of hominin evolution in the Plio-Pleistocene. Clearly, only one could be on the main branch eventually leading to Homo sapiens. By labeling this new group Homo rather than Australopithecus, Leakey was guessing that he had found our ancestors.(with early members of genus Homo showing larger front teeth relative to back teeth and narrower premolars)

habitual bipedalism

Bipedal locomotion as the form of locomotion shown by hominins most of the time.

obligate bipedalism

Bipedalism as the only form of hominin terrestrial locomotion. Major anatomical changes in the spine, pelvis, and lower limbs are required for bipedal locomotion, so once hominins adapted this mode of locomotion, other forms of locomotion on the ground became impossible

Arabian Plate

Both of these geographical changes had significant impacts on the climate, and the early Miocene was considerably warmer than the preceding Oligocene. Moreover, by 19 mya, the Arabian Plate (which had been separate) "docked" with northeastern Africa. As a result, migrations of animals from Africa directly into southwest Asia (and in the other direction as well) became possible. Among the earliest transcontinental migrants (around 16 mya) were African hominoids that colonized both Europe and Asia at this time.

New evidence of Eocene anthropoid origins has recently been discovered in both

China and North Africa. In 2013, Xijun Ni and colleagues published on a relatively complete and partially articulated specimen from China that may be ancestral to the modern-day tarsier.

hominins

Colloquial term for members of the tribe hominini, which includes all bipedal hominoids back to the divergence with African great ape

Archicebus achilles

Dating to 55 mya, Archicebus achilles is now the oldest known haplorhine primate, suggesting that the tarsier and anthropoid lineages may have already split by the early Eocene. Archicebus likely weighed 20 to 30 g, about the size of a modern pygmy mouse lemur, and tooth morphology suggests that it ate insects. Many of the features of the skull, teeth, and limbs are similar to those of modern tarsiers, whereas the foot elements are more anthropoid-like (Ni et al., 2013). Its long tail and hind limbs suggest that it was a tree-dwelling primate, and its small eye orbits indicate that it was diurnal, unlike modern tarsiers, which are active at nigh

Miocene Fossil hominoids: Closer Connections to Apes and humans

During the approximately 18 million years of the Miocene (23-5 mya), a great deal of evolutionary activity took place. in fact, the Miocene could be called "the golden age of hominoids." Many thousands of fossils have been found from dozens of sites scattered in East Africa, southern Africa, southwest Asia, into western and southern Europe, and extending into southern Asia and China. During the Miocene, significant transformations relating to climate and repositioning of landmasses took place. By 23 mya, major continental locations approximated those of today (except that North and South America were separate)

benefits of bipedalism

First of all, bipedal locomotion freed the hands for carrying objects and for making and using tools. . Such early cultural developments had an even more positive effect on speeding the development of yet more efficient bipedalism—once again emphasizing the dual role of biocultural evolution. open (or semi-open) terrain, early spotting of predators (particularly large cats, such as lions, leopards, and sabertooths) would be of critical importance. We know that modern ground-living primates, including savanna baboons and vervets, occasionally adopt this posture to "look around" when out in open country. Moreover, bipedal walking is an efficient means of covering long distances, and when large game hunting came into play (several million years after the initial adaptation to ground living), further refinements increasing the efficiency of bipedalism may have been favored. It's hard to say exactly what initiated the process, but all these factors probably played a role in the adaptation of hominins to their special niche through a special form of locomotion.

Aramis

From another million years or so later in the geological record in the Middle Awash region, a very large and significant assemblageiometric dating firmly places these remains at about 4.4 mya. The site, represented by a 6-fo of fossil hominins has been discovered at a site called. radiometric dating firmly places these remains at about 4.4 mya. The site, represented by a 6-foot-thick bed of bones, has yielded more than 6,000 fossils. From this key site, excavations reveal both large and small vertebrates—birds and other reptiles and even very small mammals. Additionally, fossil wood and pollen samples have been recovered. All this information is important for understanding the environments in which these ancient hominins lived.

dating back to almost 50 mya

Hominins, of course, evolved from earlier primates

Malapa Discoveries

However, new and remarkably well-preserved fossil discoveries from South Africa may challenge this view. In 2008, paleoanthropologists discovered two partial skeletons at the Malapa Cave, located just a few miles from Sterkfontein and Swartkrans. Actually, the first find was made by the lead researcher's 9-year-old son, Matthew. His father (Lee Berger, from the University of Witwatersrand) and colleagues have been further investigating inside the cave, where several skeletons may be buried, and they announced and described these finds in 2010 (Berger et al., 2010). Current interpretations of the site context suggest that the two individuals likely fell through a fissure into a deep cave shaft (Dirks et al, 2010). Using paleomagnetic dating as well as more precise radiometric techniques than have been used before in South Africa (Dirks et al., 2010; Pickering et al., 2011), the fossils are dated to just a little less than 2 mya and show a fascinating mosaic of more primitive australopith characteristics along with a few derived features more suggestive of Homo.

Sonia Harmand

In 2011, crude stone tools were discovered by Sonia Harmand at the site of Lomekwi 3, located along the western shore of Lake Turkana, Kenya. Analyses by Harmand and colleagues (2015) of the tools and the geological deposits they are found in suggest that the tools date to 3.3 mya. If the geological context is correct, these finds would push back the date of the earliest stone tools approximately 700,000 years earlier than the Oldowan tools from Gona, Ethiopia. However, there is some disagreement over the association of the stone tools and the deposits at Lomekwi 3, so more research is needed to substantiate the dates of these early tools. Beginning around 1.4 mya, some Oldowan tool types began to be replaced with larger, more complex stone tools (although many Oldowan tools continued to be produced as well).

ossae coxae vs human spine and pelvis comparison

In a quadruped, the ossa coxae are vertically elongated bones positioned along each side of the lower portion of the spine and oriented more or less parallel to it. In hominins, the pelvis is comparatively much shorter and broader and extends around to the side. This configuration helps to stabilize the line of weight transmission in a bipedal posture from the lower back to the hip joint

australopiths are made of what 2 genera

In fact, this diverse and very successful group of hominins is made up of two closely related genera, Australopithecus and Paranthropus.

One of the essentials of paleoanthropology is placing sites and fossils into a chronological time sequence.

In other words, we want to know how old they are. How, then, do we date fossils—or, more precisely, how do we date the geological settings in which they are found? The question is important, so let's examine some of the dating techniques used by paleontologists, geologists, and paleoanthropologists.

recent discoveries

In the last several years, detailed molecular evidence clearly shows that the great apes (traditionally classified as pongids and including orangutans, gorillas, chimpanzees, and bonobos) don't make up a coherent evolutionary group sharing a single common ancestor. Indeed, the molecular/genetic data indicate that the African great apes (gorillas, chimpanzees, and bonobos) are significantly more closely related to humans than is the orangutan. What's more, at an even closer evolutionary level, we now know that chimpanzees and bonobos are yet more closely connected to humans than are gorillas. Hominoid classification has been significantly revised to show these more complete relationships, and two further taxonomic levels (subfamily and tribe) have been added

landmasses effect eocene animals

It's important to recall that the landmasses that connect continents, as well as the water boundaries that separate them, have an obvious impact on the geographical distribution of all land animals, including primate

African forms(23-14mya)

Known especially from western Kenya, these include quite generalized, and in many ways primitive, hominoids. The best-known genus is Proconsul. In fact, Proconsul isn't much like an ape, and postcranially it more closely resembles a monkey. But there are some derived features of the teeth that link Proconsul to hominoids.

European forms(16-11mya)

Known from widely scattered localities in France, Spain, Italy, Greece, Austria, Germany, and Hungary, most of these forms are quite derived. However, this is a varied and not well-understood group. The best known of these are placed in the genus Dryopithecus; the Hungarian and Greek fossils are usually assigned to other genera. The Greek fossils, called Ouranopithecus, date to 10-9 mya. Evolutionary relationships are uncertain; some researchers have suggested a link with the African ape-hominin group, but most primatologists think these similarities result from homoplasy (Wood and Harrison, 2011; see Chapter 5).

sites

Locations of discoveries. in paleontology and archaeology, a site may refer to a region where a number of discoveries have been made.

the way scientist double check dating

Many of the techniques just discussed are used together to provide independent checks for dating important early hominin sites. Each technique has a degree of error, and only by cross-correlating the results can paleoanthropologists feel confident about dating fossil and archaeological remains. This point is of the utmost importance, for a firm chronology forms the basis for making sound evolutionary interpretations

Only hominins

Modifying rocks according to a consistent plan or simply carrying them around from one place to another over fairly long distances (in a manner not easily explained by natural means, such as streams or glaciers) is characteristic of no other animal but hominins.

Eocence relation to primates of today

Nevertheless, some fossil finds from late in the Eocene have derived features (such as a dental comb) that link them to modern lemurs and lorises.

Where was Lucy found?

One extraordinary discovery at Hadar is the Lucy skeleton (Fig. 8-24), found eroding out of a hillside by Don Johanson. This fossil is scientifically designated as Afar Locality (AL) 288-1, but is usually just called Lucy (after the popular Beatles song "Lucy in the Sky with Diamonds"). Representing almost 40 percent of a skeleton, this is one of the most complete individuals from anywhere in the world for the entire period before about 100,000 years ago

In fact, there were at least three separate lineages of hominins living (in some cases side by side) between 2 and 1.2 mya.

One of these is a later form of Australopithecus; another is represented by the highly derived three species that are often assigned to the genus Paranthropus; and the last consists of early members of the genus Homo

the earliest hominins were confined to where?

One thing is certain, however. The earliest members of the human family were confined to Africa. Only much later did their descendants disperse from the African continent to other areas of the Old World.

Real artifacts

Only rocks that have been altered according to a regular pattern are identifiable to us as real artifact

the mode of locomotion

Our mode of locomotion is indeed extraordinary, involving, as it does, a unique kind of activity in which "the body, step by step, teeters on the edge of catastrophe" (Napier, 1967, p. 56). The problem is to maintain balance on the "stance" leg while the "swing" leg is off the ground. In fact, during normal walking, both feet are simultaneously on the ground only about 25 percent of the time, and as speed of locomotion increases, this percentage becomes even smaller. Maintaining a stable center of balance calls for many drastic structural/anatomical alterations in the basic primate quadrupedal pattern. Moreover, the foot must act as a stable support instead of a grasping limb. When we walk, our foot is used like a prop, landing on the heel and pushing off on the toes, particularly the big toe. In addition, our legs became elongated to increase the length of the stride. An efficient bipedal adaptation required further anatomical changes to the lower limb to allow full extension of the knee and to keep the legs close together during walking, in this way maintaining the center of support directly under the body.

Mary and Louis Leakey

Owing to the pioneering research of Mary and Louis Leakey, this area has provided the most detailed information from anywhere in the world about early hominin tool use. Mary Leakey in particular, dedicated her career to excavating early hominin sites and analyzing ancient artifacts and the hominins who made them

Paranthropus robustus

Paranthropus fossils have also been found at several sites in South Africa. As we discussed earlier, the geological context in South Africa usually does not allow as precise chronometric dating as is possible in East Africa. Based on these less precise dating methods, Paranthropus in South Africa dates to about 2-1.2 mya. Paranthropus in South Africa is very similar to its close cousin in East Africa, but it's not quite as dentally robust. As a result, paleoanthropologists prefer to regard South African Paranthropus as a distinct species—one called Paranthropus robustus.

Paranthropus diet

Paranthropus was adapted for a diet emphasizing rough vegetable foods. However, this does not mean that these very large-toothed hominins did not also eat a variety of other foods, perhaps including some meat. In fact, sophisticated recent chemical analyses of Paranthropus teeth suggest that their diet may have been quite varied

Multidisciplinary

Pertaining to research involving mutual contributions and cooperation of experts from various scientific fields (i.e., disciplines).

Plio-Pleistocene

Pertaining to the Pliocene and first half of the Pleistocene, a time range of 5-1 mya. For this time period, numerous fossil hominins have been found in Africa.

Literally thousands of footprints have been found at Laetoli, representing more than 20 different kinds of animals

Pliocene elephants, horses, pigs, giraffes, antelopes, hyenas, and an abundance of hares

Australopithecus afarensis

Slightly later and much more complete remains of Australopithecus have come primarily from the sites of Hadar (in Ethiopia) and Laetoli (in Tanzania). Much of this material has been known for four decades, and the fossils have been very well studied; indeed, in certain instances, they are quite famous. For example, the Lucy skeleton was discovered at Hadar in 1974, and the Laetoli footprints were first found in 1978. These hominins are classified as members of the species Australopithecus afarensis

history of hominins is hard to discover without tool

Still, when we examine the archaeological record of earlier hominins, what's available for study is almost exclusively limited to material culture, especially the bits and pieces of broken stone left over from tool manufacture. This is why it's extremely difficult to learn anything about the earliest stages of hominin cultural development before the regular manufacture of stone tools. As you'll see, this most crucial cultural development has been traced to approximately 2.6 mya in East Africa (Semaw et al., 2003). Yet because of our contemporary primate models, we can assume that hominins were undoubtedly using other kinds of tools (made of perishable materials) and displaying a whole array of other cultural behaviors long before then.

The best strata for data comes from

Strata that provide the best samples for K/Ar dating are those that have been heated to an extremely high temperature, such as that generated by volcanic activity. Heating drives off previously accumulated argon gas, thus "resetting" the clock to zero. As the material cools and solidifies, 40K continues to break down to 40Ar, but now the gas is physically trapped inside the cooling material. To date the geological material, it is reheated, and the escaping gas is then measured. Potassium-argon dating has been used to date very old geological events—such as the age of the earth— as well as those less than 2,000 years old. Another radiometric dating method, this one measuring the decay of uranium into lead (the U/Pb method, with a half-life of 4.47 billion years), has been used recently in South Africa to date hominin sites

problems with stratigraphic dating.

Stratigraphic dating does, however, have a number of potential problems. Earth disturbances, such as volcanic activity, river action, and faulting, may shift the strata or materials in them, and the chronology may be difficult or impossible to reconstruct. What's more, given the widely different rates of accumulation, the elapsed time of any stratum cannot be determined with much accuracy.

Oligocene Primates: Anthropoid Connections

The Oligocene (33-23 mya) has yielded numerous additional fossil remains of several different early anthropoid species. Most of these are Old World anthropoids, all discovered at a single locality in Egypt, the Fayum . In addition, there are a few known fossil fragments from North and South America that relate only to the ancestry of New World monkeys. By the early Oligocene, continental drift had separated the New World (that is, the Americas) from the Old World (Africa and Eurasia). Some of the earliest Fayum species, nevertheless, may potentially be close to the ancestry of both Old and New World anthropoids. It's been suggested that late in the Eocene or very early in the Oligocene, the first anthropoids (primitive "monkeys") arose in Africa and later reached South America by "rafting" over the water separation on drifting chunks of vegetation (Ciochon and Chiarelli, 1980; Houle, 1999; Poux and Douzery, 2004). What we call "monkey," then, may have a common Old World origin, but the ancestry of New and Old World monkeys was separate after about 35 mya. After this time, the closest evolutionary connections humans have are with other Old World anthropoids, that is, with Old World monkeys and apes

the way to identify hominins

The central task, then, in trying to understand the earliest members of the hominin lineage is to identify anatomical features that indicate bipedalism and to interpret to what degree these individuals were committed to this form of locomotion (that is, was it a habitual or obligate biped?).Only after around 4 mya do we see all the major structural changes required for bipedalism

where does the earliest hominins date back to

The earliest evidence of hominins dates to the end of the Miocene and mainly includes dental and cranial fragments.

Plesiadapiforms

The earliest possible primates date to the Paleocene (65-56 mya) and belong to a large and diverse group of primitive mammals.

rare parts of skeleton to find

The fact that remains of the postcranial skeleton are preserved is potentially crucial, because key body elements, such as the pelvis and the foot, are only very rarely discovered, in part due to their low bone density.

more than 6 mya

The first hominins appeared in Africa more than 6 mya

the black skull

The first member of the Paranthropus evolutionary group (clade) comes from a site in northern Kenya on the west side of Lake Turkana. This key find is that of a nearly complete skull, called the "Black Skull" (owing to manganese staining during fossilization), and it dates to approximately 2.5 mya. This skull, with a cranial capacity of only 410 cm3, is among the smallest for any hominin known, and it has other primitive traits reminiscent of A. afarensis. However, here's what makes the Black Skull so fascinating: Mixed into this array of distinctively primitive traits are a host of derived ones that link it to other, later Paranthropus species (including broad face, a very large palate, and a large area for the back teeth

Asian forms(15-5mya)

The largest and most varied group of Miocene fossil hominoids was geographically dispersed from Turkey through India/Pakistan and east to Lufeng, in southern China. The best-known genus is Sivapithecus (from Turkey and Pakistan), and fossil evidence indicates that most of these hominoids were highly derived.

Ardipithecus

The last group of possible hominins dating to the late Miocene (that is, earlier than 5 mya) comes from the Middle Awash in the Afar Triangle of Ethiopia. Radiometric dating places the age of these fossils in the very late Miocene, 5.8-5.2 mya. The fossil remains themselves are very fragmentary. Some of the dental remains resemble some later fossils from the Middle Awash (discussed shortly), and Yohannes Haile- Selassie, the researcher who first found and described these earlier materials, has provisionally assigned them to the genus

Darwinius masillae

The most complete early primate fossil ever found was announced in 2009 and, in honor of the 200th anniversary of Darwin's birth, is called Darwinius masillae It comes from the Messel site in Germany, dates to 47 mya (during the Eocene), and is extraordinarily well preserved (Franzen et al., 2009). At the time of its announcement, it created a public sensation, although the find has a complex and somewhat peculiar history. virtually no other experts in early primate evolution have had an opportunity to see the original fossil, and thus the wide publicity it received wasn't accompanied by the normal assessments of other researcher

Pre-Australopiths (6+-4.4 mya)

The oldest and most surprising of these earliest hominins is represented by a cranium discovered at a Central African site called Toros-Menalla in the modern nation of Chad (Brunet et al., 2002; Fig

where do the roots of primate order go back to?

The roots of the primate order go back to the early stages of the placental mammal radiation at least 65 mya. From this fact you can see that the earliest primates evolved from early and still primitive placental mammals

Aegyptopithecus

This genus is represented by several well-preserved crania and abundant jaws and teeth. The largest of the Fayum anthropoids, Aegyptopithecus is roughly the size of a modern howler monkey (13 to 18 pounds; Fleagle, 2013) and is thought to have been a short- limbed, slow-moving arboreal quadruped. Aegyptopithecus is important because, better than any other known form, it bridges the gap between the Eocene fossils and the succeeding Miocene hominoidst. Aegyptopithecus is a very primitive Old World anthropoid, with a small brain and long snout and not showing any derived features of either Old World monkeys or hominoids. Found in geological beds dating to 35-33 mya,

stratigraphic dating

This was one of the first techniques used by scholars working with the vast expanses of geological time. Stratigraphic dating is based on the law of superposition, which states that a lower stratum (layer) is older than a higher one. Given the fact that much of the earth's crust has been laid down by layer after layer of sedimentary rock, stratigraphic relationships have provided a valuable tool in reconstructing the history of the earth and of life upon it. We may not know the date (in years) of either one, but we would be able to infer a relative sequence. This method of dating is based on stratigraphy and is called stratigraphic dating.

chronometric techniques

To determine age as precisely as possible, scientistsnhave developed a variety of chronometric techniques, many based on radioactive decay. The principle is quite simple: Radioactive isotopes of certain elements are unstable, and they decay to form an isotopic variant of another element. Because the rate of decay is known, the radioactive material serves as an accurate geological clock. By measuring the amount of decay in a particular sample, scientists have devised techniques for dating the immense age of the earth (and of moon rocks) as well as material only a few hundred years old. The most important chronometric technique used to date early hominins involves potassium-40 (40K) which has a half-life of 1.25 billion years and produces argon-40 (40Ar).

Eocene Primates: Closer Connections to Living Primates

Unlike the available Paleocene forms, those from the Eocene display more clearly derived primate features. These fossils have been found at many sites in North America and Europe (which for most of the Eocene were still connected). In addition, more recent finds have shown that the radiation of Eocene primates extended to Asia and Africa.

bipedal locomotion

Walking on two feet. Walking on two legs is the single most distinctive feature of the hominins

Afarensis

afarensis was not bipedal in quite the same way that modern humans are. From detailed comparisons with modern humans, estimates of stride length, cadence, and speed of walking have been ascertained, indicating that the Laetoli hominins moved in a slow-moving ("strolling") fashion with a rather short stride. Several hundred A. afarensis specimens, representing a minimum of 60 individuals (and perhaps as many as 100), have been excavated from Laetoli and Hadar. Without question, A. afarensis is more primitive than any of the other later australopith fossils from South or East Africa (discussed shortly). By "primitive" we mean that A. afarensis retains more ancestral features compared with later-occurring hominin species. That is, A. afarensis shares more primitive features with late Miocene apes and with living great apes than do later hominins, who display more derived characteristics. he teeth of A. afarensis are quite primitive. The canine teeth are often large and pointed, which are apelike traits. Moreover, the lower first premolar provides a shearing surface for the upper canine (although it is not a full honing complex as seen in many monkeys and apes). Lastly, the tooth rows are parallel

There are two major subgroups of australopiths,

an earlier one that is more anatomically primitive and a later one that is much more derived. These earlier australopiths, dated 4.2-3 mya, show several more primitive (ancestral) hominin characteristics than the later australopith group, whose members are more derived, some extremely so. These more derived hominins lived after 2.5 mya and are composed of two different genera, together represented by at least five different species

well-preserved hominin footprints

are extremely important in furthering our understanding of human evolution. For the first time, we can make definitive statements regarding the locomotor pattern and stature of early hominins. Studies of these impression patterns clearly show that the mode of locomotion of these hominins was bipedal (Day and Wickens, 1980).

characteristics used to identify hominins

characteristics as bipedal locomotion, large brain size, and tool- making behavior as being significant (at some stage) in defining what makes a hominin a hominin and dental

The most immediately obvious feature distinguishing the H. habilis material from the australopiths is

cranial size.

Paleoanthroplogy is a

diverse multidisciplinary pursuit seeking to reconstruct every possible bit of information concerning the dating, anatomy, behavior, and ecology of our hominin ancestors. In the past few decades, the study of early hominins has marshaled the specialized skills of many different kinds of scientists.This growing and excitng adventure includes, but is not limited to, geologists, vertebrate paleontologists, archaeologists, physical anthropologists, and paleoecologists.

Geologists, usually working with other paleoanthropologists

do the initial survey to locate potential early hominin sites. Many sophisticated techniques can contribute to this search, including aerial and satellite photography. Vertebrate paleontologists are usually also involved in this early survey work, for they can help find geological beds containing faunal remains. Paleontologists can also (through comparison with known faunal sequences) assign approximate ages of fossil sites in the field without having to wait for the expensive and time-consuming chronometric analyses.

the first hominin discovery in africa

from the Taung site, discovered back in 1924. The discovery of the beautifully preserved child's skull from Taung is a fascinating tale. When first published in 1925 by a young anatomist named Raymond Dart, most experts were unimpressed. They thought Africa to be an unlikely place for the origins of hominins.

Paranthropus

genus. The most derived australopiths are the various members of Paranthropus. Though all australopiths have large teeth, Paranthropus has the largest teeth of all, especially as seen in its huge premolars and molars. Along with their massive back teeth, these hominins show a variety of other specializations related to powerful chewing. For example, they all have large, deep lower jaws and large attachments for muscles associated with chewing. In fact, these chewing muscles are so prominent that major anatomical alterations evolved in the architecture of their face and skull vault. In particular, the Paranthropus face is flatter than that of any other australopith; the broad cheekbones (to which the masseter muscle attaches) flare out;

stratum (pl., strata)

geological layer

Recent discoveries from the Rukwa Rift Basin in Tanzania

have also found possible evidence for the divergence of Old World monkeys and hominoids in the late Oligocen

Bipedalism is only seen in

hominins

Biostratigraphy

is based on the fairly regular changes seen in the dentition and other anatomical structures in such groups as pigs, rodents, and baboons. Dating of sites is based on the presence of certain fossil species that also occur elsewhere in deposits whose dates have been determined. This technique has proved helpful in cross-correlating the ages of various sites in the southern, central, and eastern regions of Africa.

Paleomagnetism

is based on the shifting nature of the earth's geomagnetic pole. Although now oriented northward, the geomagnetic pole is known to have shifted several times in the past and at times was oriented to the south. By examining magnetically charged particles encased in rock, geologists can determine the orientation of these ancient "compasses." This technique doesn't provide exact dates but is used to double-check other techniques

Paleoanthropology

is defined as the study of early humans.

Orrorin

is the pre-australopith generally recognized as having the best evidence to establish it as a hominin among all late Miocene-age fossils. a. The earlier of these finds (dated by radiometric methods to around 6 mya) comes from the Tugen Hills and includes mostly dental remains, but also some quite complete lower limb bones. The fossils have been placed in a separate early hominin genus called Orrorin. The postcranial remains are especially important, because they seem to indicate bipedal locomotion (Pickford and Senut, 2001; Senut et al., 2001; Galik et al., 2004; Richmond and Jungers, 2008). As a result of these further analyses, Orrorin is the pre-australopith generally recognized as having the best evidence to establish it as a hominin among all late Miocene-age fossils.

artifacts

objects or materials made or modified for use by hominins. the earliest artifacts tend to be made of stone or occasionally bone.

Material culture

or the tools humans use—is but a small portion of this cultural complex

The fundamental basis for human cultural success relates directly to

our cognitive abilities.

A. afarensis had a small brain

probably averaging for the whole species not much over 420 cm3.

chronometric (chronos, meaning "time," and metric, meaning "measure")

referring to a dating technique that gives an estimate in actual numbers of years.

postcranial

referring to all or part of the skeleton not including the skull. the term originates from the fact that in quadrupeds, the body is in back of the head; the term literally means "behind the head."

faunal

referring to animal remains; in archaeology, specifically refers to the fossil (skeletonized) remains of animals

Lemurs, lorises, tarsiers, monkeys, and apes all spend considerable time

sitting erect while feeding, grooming, or sleeping.

stratigraphy

study of the sequential layering of geological deposits

thermoluminescence(TL)

technique for dating certain archaeological materials that were heated in the past (such as stone tools) and that release stored energy of radioactive decay as light upon reheating.

Relative dating methods

tell you that something is older or younger than something else, but not by how much. If, for example, a fossil cranium is found at a depth of 50 feet and another one at 70 feet at the same site, we usually assume that the cranium at 70 feet is older.

2.6 mya

the age of the oldest clearly identified human artifacts

Himalayan Plateau

the continued collision between the South Asian Plate and southern Asia produced this

Oldowan Industry

the earliest recognized stone tool culture, including very simple tools, mostly small flakes

the way hominins nature is revealed

the hominin nature of these remains is revealed by more than the morphological structure of teeth and bones; in many cases, we know that these animals are hominins also because of the way they behaved—emphasizing once again the biocultural nature of human evolution.

honing complex

the shearing of a large upper canine with the first lower premolar, with the wear leading to honing of the surfaces of both teeth. this anatomical pattern is typical of most old World anthropoids, but is mostly absent in hominins

large-bodied hominoids

those hominoids including the great apes (orangutans, chimpanzees, gorillas) and hominins, as well as all ancestral forms back to the time of divergence from small-bodied hominoids (i.e., the gibbon lineage) in the late Miocene (see pp. 209-214 for further discussion). As we shall see shortly, the most fundamental feature of the early hominins is the adaptation to bipedal locomotion. In addition, recently discovered Miocene remains of the first fossils linked closely to gorillas (Suwa et al., 2007) provide further support for a late Miocene divergence (about 10-7 mya) of our closest ape cousins from the hominin line. The only fossil chimpanzee so far discovered has a much later date of around 500,000 years ago (ya), long after the time that hominins split from African apes (McBrearty and Jablonksi, 200

The pelvic girdle is composed of three elements:

two hip bones, or ossa coxae (sing., os coxae), joined at the back to the sacrum

summary of main topics

• The earliest primitive primates appear to have evolved during the Paleocene around 65 mya. • Many primate fossil forms more similar to living primates evolved in the Eocene (56-33 mya). Most of these species went extinct, although some show connections to modern lemurs/lorises or tarsiers. •The first anthropoids likely appear in the late Eocene, but are much better documented from the Oligocene site known as the Fayum, in Egypt (about 33 mya) •Large-bodied hominoids are wide- spread and diverse in the Old World throughout the entire Miocene (23-5 mya) • Paleoanthropology is the multi-disciplinary science that studies early human evolution. • Accurately dating early hominins is essential, and there are two major types of dating techniques: relative and chronometric • The first hominins appear 7-6 mya and for the next 5 million years are all restricted to Africa. • Many species of these early African hominins have been identified and can be summarized within three major subgroups: - Pre-australopiths(6+-4.4mya) Including three genera of very early, and still primitive (possible) hominins: Sahelanthropus, Orrorin, and Ardipithecus - Australopiths (4.2-1.2 mya) Early, more primitive australopith species (4.2-3 mya), including Australopithecus anamensis and Australopithecus afarensis - Later, more derived australopith species (2.5-1.2 mya), including two genera: Paranthropus and a later species of Australopithecus - EarlyHomo(2.4-1.4mya) The first members of our genus, who around 2 mya likely diverged into more than one species