Human Evolution: Our Ancestors

We did not descend from chimpanzees or apes but we did evolve from common ancestors. The change was not sudden but rather it took millions of years of slow evolutionary changes. During the long transition there have been many known key stages in the fossil record known as "transitional fossils." These fossils make up our hominid family legacy.

A phylogenetic tree is a graphical means to depict the evolutionary relationships of a group of organisms. The phylogenetic tree to the left shows one reconstruction of the relationships among early human species, as we best know them today. With so many various species of hominids discovered, and many more left to be discovered, it is difficult to know for sure which species descended from which branch of the hominid family tree. Thanks to known time periods of when each specimen lived along with other clues such as changes of physical structure and locations we can piece together a pretty accurate phylogenetic tree of our ancestors.

A few of our distant evolutionary ancestors

Gigantopithecus blacki

Basic Info

Description

Evidence

Meaning: 'Gigantic Ape of Black' after the 20th century archaeologist Davidson Black. Lived: 6.3 million – 200,000 years ago. Range: South East Asia. Diet: Bamboo, durian, jackfruit. Size: 300 cm / 544 kg. Standing an enormous 3 metres (9’10”) in height, Gigantopithecus may be the largest primate ever to have walked the Earth. It fed on bamboo in the dense forests of South East Asia. Gigantopithecus had a broad, short face with a massive jaw and teeth designed for stripping bamboo shoots. Like other big herbivores, Gigantopithecus was probably a slow mover. But it had little need for speed. Its feeding habits required it to do little more than move from place to place as it systematically stripped vegetation from its surroundings. Homo erectus may have hunted and eaten juvenile or injured Gigantopithecus, but it is unlikely they would have taken on an enormous adult. Gigantopithecus males were much larger than the females, suggesting there may have been strong competition for mates amongst males. Dr Russell Ciochon of the University of Iowa and primate specialist Bill Munns calculated Gigantopithecus’ height at 3 metres (9’10”). Ciochon and Munns estimated the size of its head from its jaw and then used a head/body ratio of 1:6.5 to determine the size of its body. They originally tried a head/body ratio of 1:7, but the resulting body looked too small in comparison with its head. Gigantopithecus teeth also show a high incidence of hypoplasia: pitting in the tooth enamel that indicates periods of poor health. This may have resulted from disease, or from a food shortage. Bamboo, the giant ape’s staple diet, is subject to periodic die-offs. Today, this can force animals that feed on the plant, like giant pandas, to the brink of starvation. These periodic die-offs may also explain why Gigantopithecus may have suffered from poor health.

Australopithecus afarensis

Basic Info

Description

Evidence

Meaning: 'Southern Ape of Afar' after the Afar region of Ethiopia. Lived: 3.9 - 3.0 million years ago. Range: East Africa. Diet: Soft fruit, nuts, seeds, tubers and bird eggs. Size: M: 152cm / 45kg F: 107cm / 28 kg. Brain Size: 35% the size of a modern brain. Australopithecus afarensis walked upright like a human, but its body proportions were like those of a chimpanzee. Like chimps, afarensis had a small brain, long, dangly arms, short legs and a cone-shaped torso with a large belly. Around 3.2 million years ago, this bipedal ape roamed a mixed habitat of savannah and woodland beside lakes and floodplains. It foraged for fruit, seeds and nuts and may even have eaten some meat. Australopithecus afarensis probably climbed into trees to avoid sabre-toothed cats like Dinofelis and to sleep in safety at night. This hominid seems to have lived in social groups of between 20 and 30. These groups were probably like those of chimpanzees, with dominance hierarchies in which each individual knows their place. Male afarensis probably cooperated to drive away predators. Once mature, females may have joined other troops of afarensis. On 24 November 1974 in the Afar region of Ethiopia, anthropologists Donald Johanson and Tom Gray made one of the most famous fossil discoveries ever. While out fossil hunting in sandy ravines near the River Awash, they discovered a 40% complete skeleton dating to 3.2 million years ago. They named the find 'Lucy'. Lucy's species, Australopithecus afarensis, have small canine teeth compared with apes. This suggests males may have been cooperating. Examinations of Lucy's knee joint and pelvis demonstrate that she walked upright. And footprints left in volcanic tuff at Laetoli in Tanzania by afarensis suggest it walked with a human-like stride. In 1975 Michael Bush, a student of Johanson's, discovered the fossilised remains of over 13 afarensis individuals buried together in a possible flash flood. The remains show a mixed group of young and old, male and female. The individuals may have been related to each other and the find has been dubbed 'The First Family.'

Paranthropus boisei

Basic Info

Description

Evidence

Meaning: 'Near man of Boise' after Charles Boise, financial patron of the Leakey family. Lived: 2.3 - 1.2 million years ago. Range: East Africa (Ethiopia, Tanzania, and Kenya). Diet: Nuts, tubers, termites, possibly papyrus rhizomes. Size: M: 137cm / 49kg F: 124cm / 34kg Brain Size: 39% the size of a modern brain. This vegetarian apeman had a big, flat face with a massive jaw. It lived at a time when forests were vanishing from East Africa, creating a shortage of food such as soft fruit. Paranthropus boisei coped with the shortage by evolving a massive jaw and huge teeth to chomp tough-to-chew foods such as nuts, roots, seeds and tubers. These hard, gritty foods were more abundant in the open woodland and grasslands that boisei called home. Paranthropus boisei may have lived in groups organized in harems, in which one male mated with many females. Males were easy to spot amongst a harem of females; they were much more muscular with much bigger faces. In July 1959, Mary Leakey unearthed the complete skull of a male hominid with a massive jawbone at Olduvai Gorge, Tanzania. Leakey named the fossil 'Zinjanthropus' after 'Zinj,' an ancient name for East Africa. The species was later reassigned to Australopithecus, and more recently to Paranthropus. Fossilised boisei teeth, jawbones, skulls and limbs have since been recovered from a wide area including Lake Turkana and Koobi Fora in Kenya, Olduvai George in Tanzania and Omo and Konso in Ethiopia. Wear patterns on boisei's tooth enamel show that it devoured hard, gritty food. And the high levels of a carbon isotope carbon-13 in their teeth suggest they may have been eating the roots of the papyrus plant. Male boisei were much bigger than the females, a phenomenon called sexual dimorphism. Like modern gorillas, another dimorphic species, boisei males may have developed large bodies to compete with each other for access to large groups, or harems, of females.

Homo rudolfensis

Basic Info

Description

Evidence

Meaning: 'Rudolf Man'. Lived: 2.4 - 1.9 million years ago. Range: East Africa. Diet: Omnivorous diet. Size: M: 160cm / 60kg F: 150cm / 51kg. Brain Size: 56% the size of a modern brain. Homo rudolfensis may have lived over a wide area of East Africa, from Ethiopia in the north to Malawi in the south. They were very tall, towering above other hominids alive at the time – especially the stumpy Homo habilis. Their faces were large and flat in comparison with those of habilis, with flared cheekbones and big molar teeth. Like Homo habilis, rudolfensis probably combined foraging with scavenging meat from animal carcasses. This may have put the two species in competition with each other. The large body size of rudolfensis may have made it more effective at scaring away other animals from kills, turning it into an effective scavenger. The type (or original) specimen of Homo rudolfensis is a toothless skull known as KNM-ER-1470, discovered by Bernard Ngeneo at Koobi For a, Kenya. The name rudolfensis was first used by the Russian anthropologist V. P. Alexeev who, in 1975, suggested that the 1470 skull should be placed in a new family called Pithecanthropus rudolfensis. But in 1986, the anthropologist Bernard Wood suggested the name Pithecanthropus be dropped in favour of Homo. Although its teeth are within the size range of the australopithecines, rudolfensis possessed a large brain of around 752 cubic centimetres (cc). Two large femurs found nearby the 1470 skull suggest rudolfensis had a taller, more modern physique than habilis. However, in 2003, Professor Robert Blumenschine of Rutgers University, New Jersey found new fossils at Olduvai Gorge in Tanzania that cast doubt on the validity of rudolfensis as a separate species.

Homo habilis

Basic Info

Description

Evidence

Meaning: 'Handy man'. Lived: 2.2 - 1.6 million years ago. Range: Eastern and southern Africa. Diet: Omnivorous diet. Size: M: 131cm / 37kg F: 100cm / 32 kg. Brain Size: 47% the size of a modern brain. Homo habilis had a short body and long ape-like arms like the australopithecines. But they were distinguished from earlier hominids by their big brain (c. 630 cubic centimetres) and small teeth. The species evolved in Africa at a time when traditional forest foods like fruit were becoming scarce forcing animals to seek out new nutritional sources. Homo habilis ate meat by scavenging from animal carcasses. But snatching meat from under the noses of fearsome predators like lions was a risky business. However, Homo habilis had a secret weapon: stone tools. Crude stone implements were used to smash open animal bones and extract the nutritious bone marrow. Homo habilis lived in East Africa at the same time as Paranthropus boisei. But they they occupied different ecological niches and so were not direct competitors. While habilis was an omnivore, boisei survived on a hard-to-chew vegetarian diet. Homo habilis seems to have used crude stone tools known as Oldowan tools to scavenge meat from animal carcasses. This kickstarted an increase in brain size. Meat, particularly bone marrow, contains long-chain fatty acids that are essential for brain growth. Homo habilis is known from a variety of scattered remains across East Africa. The species is known from a juvenile skull called OH7 found in 1960 at Olduvai Gorge, Tanzania by Louis Leakey. Hand bones found with this skull suggest a precision grip, a finger and thumb formation that would have allowed habilis to strike stones accurately to make tools. A partial foot skeleton, also from Olduvai Gorge, known as OH8 shows a completely modern type of bipedalism.

Homo ergaster (erectus)

Basic Info

Description

Evidence

Meaning: Homo ergaster - 'Workman' / Homo erectus - 'Upright man' Lived: ergaster - 1.9 - c.600,000 years ago / erectus - 1.8 million - c.30,000 years ago. Range: Africa, Asia, one example in Europe. Diet: Omnivorous with large quantities of meat. Size: M: 180 cm / 66 kg. F: 160 cm / 56 kg. Brain Size: 74% the size of a modern brain. Homo ergaster was tall and muscular. Slim hips and long legs enabled this species to walk long distances. Their skin was smooth to cool themselves through sweating, meaning they no longer had to pant to keep cool. Homo ergaster probably obtained food by scavenging or by chasing animals across the savannah until they died from exhaustion. This species was amongst the first to leave Africa and colonize other continents. After ergaster leaves Africa, it becomes known as Homo erectus. In Asia, Homo erectus lived in the bamboo forests and may have made tools such as staffs and spears from this strong, versatile material. The structure of Homo ergaster’s facial bones suggests they had a human-like nose with downward pointing nostrils. This allowed them to add moisture to exhaled air, useful for an active species roaming through dry, open terrain. Animal bones from ergaster sites have been found etched with the characteristic marks of stone tools used for butchery. Several Homo ergaster fossils have been discovered in the Lake Turkana region of Northern Kenya, including a near complete skeleton known as ‘Nariokotome Boy’. Homo erectus fossils have been found all over Asia, from Zhoukoudien in China to Sangiran on the island of Java, Indonesia.

Homo heidelbergensis

Basic Info

Description

Evidence

Meaning: 'Heidelberg Man'. Lived: 600,000 - 200,000 years ago. Range: Africa, Europe. Diet: Omnivorous with a heavy reliance on meat. Size: M: 180cm / 80kg F: 157cm / 51kg. Brain Size: 93% the size of a modern brain. Homo heidelbergensis inhabited Africa and Europe 600,000 – 200,000 years ago. Males were tall, as much as 180cm (6'0") in some cases, and very muscular. Their faces were sometimes very large, and most had projecting brow ridges and a sloping braincase that housed a brain nearly the size of a modern human's. Male heidelbergensis were noticeably bigger than the females. They were proficient hunters. In Europe, they seem to have targeted large animals to hunt. Horses, hippos and rhinos were all on the menu for heidelbergensis. About 300,000 years ago at present day Boxgrove in England, heidelbergensis manufactured huge numbers of stone tools to butcher big game animals. In 1907, a quarryman in Mauer, near Heidelberg in Germany discovered a large, fossilised jawbone. The jaw is now thought to belong to the species Homo heidelbergensis that lived in Europe and Africa. At Boxgrove in England, heidelbergensis used stone tools to butcher animals on a beach at the edge of an ancient sea. Wooden spears preserved in a bog in Germany and dated to 400,000 years ago, show that heidelbergensis was a proficient hunter. In 1976, the remains of 32 heidelbergensis individuals were discovered at the bottom of a cave shaft at Atapuerca in northern Spain. Most of the remains were from juveniles, many of whom showed signs of poor health.

Homo neanderthalensis

Basic Info

Description

Evidence

Meaning: 'Man from the Neander Valley'. Lived: 230,000-28,000 years ago. Range: Europe, Central Asia, Middle East. Diet: Relied heavily on meat. Size: M: 166cm / 77kg F: 154cm / 66kg. Brain Size: 12% larger than a modern brain. Neanderthals were as formidable as the Ice Age environment they lived in.Their short squat physique was an ideal body shape for conserving heat. But despite their small stature, they had big, powerful muscles - a sign of the demanding lifestyle they led. They looked out at their harsh world from under a bony ridge that arched across their foreheads. Set in the middle of their long faces was a long projecting nose that distanced the delicate tissues of the brain from the frozen Ice Age air. They were skilled hunters, cooperating together in hunting parties. Neanderthals exploited the natural landscape to surround their quarry and make a kill at close range. This hunting practice left many Neanderthals with painful injuries. Neanderthals were capable of speech, but their communication skills were not as advanced as our own. They also seemed to lack an understanding of abstract concepts such as art. Neanderthal fossil remains have been found all over Europe, from Portugal in the west to Uzbekistan in the east. The first Neanderthal fossils were found in 1856, when quarry workers dug up human fossil remains near Dusseldorf in Germany. At the time, the remains were thought to be those of a soldier who died in the Napoleonic Wars. Their huge muscles left deep grooves on their bones where they attached. Their bodies show a catalogue of injuries that matches the pattern seen in modern rodeo riders, perhaps suggesting that they were frequently thrown off big animals. Despite claims to the contrary, Neanderthals do not seem to have been our ancestors. Analysis of their DNA indicates that they were not closely related to us. They were probably outcompeted for resources by modern humans, who swept into Europe around 40,000 years ago. Recently discovered remains from Vindija in Croatia suggest that the last died out 28,000 years ago.

Homo sapiens

Basic Info

Description

Evidence

Meaning: 'Knowing man'. Lived: 150,000 - present. Range: Worldwide. Diet: Generalized diet. Size: M: 175 cm / 65kg F: 161 cm / 54 kg. Brain Size: c.1350cc. Our own species, Homo sapiens, evolved in Africa around 150,000 years ago. Homo sapiens have a characteristic look: their faces are small and tucked under a high, domed braincase. They have small eyebrow ridges and their lower jaw ends in a prominent chin. On average, their bodies are less muscular than those of earlier hominids. The appearance of modern humans coincides with the appearance of highly crafted tools, efficient food-gathering strategies and a complex social organisation. Early modern humans lived in mobile groups and established extensive social networks to trade goods and exchange gifts. These networks probably developed for the purpose of securing future favours when times were hard. And it seems that times were indeed hard for some of the first modern humans. During the last Ice Age, humans were pushed to the edge of extinction, perhaps by famine and drought caused by a sharp drop in global temperatures. For these early modern humans, an increased reliance on social alliances and creativity was key to their survival. A skull from Omo Kibish in Ethiopia dated to 130,000 years ago could be the earliest example of a modern human. Early modern human fossils are found at Klasies River Mouth and Border Cave in South Africa and have been dated from 120,000-100,000 years ago. The earliest modern human remains found outside Africa are those from Qafzeh Cave in Israel dating from 115,000-96,000 years ago. Patterns of genetic difference in modern humans support a recent African origin for humanity. Rebecca Cann and her colleagues at the University of Berkeley, California analysed mitochondrial DNA (mtDNA), a type of DNA that gets passed down through the maternal line, in a sample of modern humans. They found that the genetic types that had accumulated most mutations, or changes, over time were African, suggesting that African mtDNA types were older than those from elsewhere in the world. The relatively small amount of genetic diversity amongst modern humans suggests that they survived a catastrophe either before or just after they left Africa for other parts of the world.

Comparing Skulls

For sakes of holding on to ancient beliefs many Creationists preach to their followers and the public that there are no transitional fossils. They commonly claim that any hominid skulls found are iether a human skull or the skull of an ape. Let's take a closer look at some various hominid skulls side by side with that of modern man and apes so you can clearly see how different they are.

Let's take a look at what the skulls of a chimpanzee, gorilla, and modern man looks like.

Chimpanzee skull average brain size: 390 cc.

Gorilla skull average brain size: 650 cc.

Modern Man skull average brain size: 1400 cc.

The skulls above are clearly different and anyone would agree with that. Now let's take a look at the skull of the Chimpanzee, Gorilla, and Modern Man again but this time next to the skull of Homo Erectus (Upright Man).

Homo Erectus skull average brain size: 1000 cc

Chimpanzee, Gorilla, and Modern Man skull

Even with the heavy brow-ridge and lack of forehead the Homo Erectus skull is still very human looking but clearly is not that of a Modern Man, Gorilla, or Chimpanzee. The brain capacity is only about 1000 cc which is smaller than modern man yet twice the size of the Chimpanzee.

The Homo Habilis (Handy Man) skull shown below has large cheeks that are not found on the other skulls above. The larger nasal cavity and small canine teeth are two other noticeable characteristics. Its brain capacity around 700 cc, half of Modern Man and 300 less than Homo Erectus.

Homo Habilis skull average brain size: 700 cc

Chimpanzee, Gorilla, and Modern Man skull

The next homonid skull starts to have a resembles to the chimpanzee but is still clearly different. The Australopithecus Africanus skull has an elongated face and brow ridges but unlike the chimpanzee it's brain compacity is much larger. The skull also lacks the sharp canine teeth that a chimpanzee has and different cheekbones and nasal cavity. Because The Africanus is closer related to the chimp than humans it is not desinated as a "Homo" Africanus because it one of our "pre-human" ancestors.

Australopithecus Africanus average brain size: 485 cc

Chimpanzee, Gorilla, and Modern Man skull

The Australopithecus Afarensis skull (not to be confused with Australopithecus Africanus) has an average brain capacity of 415cc, just slightly larger than the Chimpanzee yet the two skull are still clearly different. They are obviously both primates and closely related but Afranensis walked upright on two legs and was fully bipedal with a modern looking knee. The Chimpanzee can only walk partially upright for a few seconds at a time due to a knee that cannot straighten out. Sticking with just the skull though, there is a large hole at the base of a skull (the foramen magnum) which the spinal cord passes through. The position of the foramen magnum shows us what angle the spinal column enters the skull and indicates if the animal stood upright or not. The foramen magnum of Afarensis is centrally positioned at the bottom of the skull indicating that it stood upright, unlike the Chimpanzee.