Two million BC

1.93 – 1.84 million years ago

Two million years ago, there were multiple hominin species in Africa. There was Homo habilis, with a larger brain than any australopithecine, but similar body size and long arms. There was also the recently discovered Australopithecus sediba, with brain not especially large, but maybe reorganized in a human direction, and teeth trending human-wards as well.

A. sediba

There were two robust species that we know of, boisei in east Africa and robustus in southern Africa. The robusts had huge premolars and molars, and enormous jaw muscles running through a large zygomatic arch to attach all the way up to the sagittal crest in the middle of the skull. Gorillas have sagittal crests too, but with them it’s about powerful bites from incisors and canines. You, on the other hand, don’t have a sagittal crest. Your temporalis muscle only runs up to your temple.

The robusts are sometimes given their own genus Paranthropus, other times included in Australopithecus. This reflects uncertainty about their relationships. Did robust morphology evolve once, with both boisei and robustus evolving from aethiopicus? Or did it evolve independently several times, with robustus evolving from Australopithecus africanus in southern Africa?

And remarkably, we now know that three different hominin genera were around not just at the same time and but in the same place, hanging around a South African cave system: Paranthropus robustus, plus Australopithecus africanus (an old-timer, with more than a million year past behind her),  plus Homo erectus (a newcomer, with a more than a million year future ahead of her).

Your cuisinart, a prehistory

A famous movie cut, from 2001: A Space Odyssey, transitions from a bone club, hurled aloft by an australopithecine 2.5 million years ago, to a spacecraft in the year 2001.

Arthur Clarke and Stanley Kubrick, coming up with the plot for the movie/book, were influenced by the popular author Robert Ardrey. In his book African Genesis, Ardrey casts human evolution as a version of the story of Cain and Abel, except in his version the peaceful vegetarians (robust australopithecines) get clobbered by the club-wielding meat-eaters (gracile australopithecines).

We were born of risen apes, not fallen angels, and the apes were armed killers besides. And so what shall we wonder at? Our murders and massacres and missiles, and our irreconcilable regiments?  Or our treaties whatever they may be worth; our symphonies however seldom they may be played; our peaceful acres, however frequently they may be converted into battlefields; our dreams however rarely they may be accomplished. The miracle of man is not how far he has sunk but how magnificently he has risen. We are known among the stars by our poems, not our corpses.

Ardrey, along with Konrad Lorenz and Desmond Morris, was much in vogue in the 1960s: Sam Peckinpah was another movie director influenced by him. The man could turn a phrase. Unfortunately his speculations on evolution and human behavior are probably not of enduring value: he had the misfortune to take up the topic too early to take on board the sociobiological revolution pioneered by William Hamilton, Robert Trivers, and George Williams, and popularized by E. O. Wilson and Richard Dawkins.

Ardrey may not have been off-base in thinking that weaponry and warfare have been an important motive force in human biological and social evolution (more on this later). But where early stone tools are concerned, a different segue, from Oldowan chopper to Cuisnart may be more appropriate.

Recent research argues that early hominins could have dramatically increased available food energy by pounding vegetables and chopping up meat into more digestible pieces. Tool use may have been an early step in our ancestors’ move to high energy diets. Meat-eating began to be important in human evolution around 2.6 million years ago. Somewhat later we see evidence that some hominins have lighter jaws and aren’t chewing as much. So to celebrate this early dietary revolution, here’s a recipe:

Steak Tartare

Place in a food processor fitted with the metal chopping blade:

1 ½ pounds lean beef (tenderloin, top round, or sirloin) cut into ½ inch cubes

Pulse until meat is coarsely ground, 7-10 seconds. Do not over-process. Remove meat to a chilled platter or individual plates and gently form into 6 individual mounds.

[Optional: Make a spoon shaped indentation on top of each mound and crack into each

1 egg yolk.]

Divide and arrange in small piles around each serving:

½ cup minced onions
½ cup minced shallots
½ cup minced fresh parsley
¼ cup minced drained capers
8-12 anchovies (optional)

Serve immediately and pass separately:

Fresh lemon juice
Worcestershire sauce
Dijon mustard
Hot pepper sauce
Freshly ground black pepper
Salt

From The Joy of Cooking 1997

Blood and brains

Humans are brainy animals. One way to show that is by looking at brain size: our species has the biggest brains, in relation to body size, of any animal. But there’s more to it than that. An earlier post covered the work of Susan Herculano-Houzel. She developed a technique for counting the number of neurons in a brain, or part of a brain. Among most mammals, big animals have a lower density of brain neurons, so they aren’t actually as brainy (measured by neuron number) as you’d think just based on their brain size. Primates however break the usual mammalian rule. Big primates have the same neuron density as little guys, so they really are quite brainy. And humans, with really big brains and (following primate rules) a high density of neurons, stand out even among primates as exceptionally brainy.

This work isn’t much help if we are looking at extinct hominins, when all we’ve got is their fossil skulls. But now there’s some interesting recent research with a new take on the subject. Brains need to be supplied with blood. The more energy they use, the more blood flow is needed. We can now figure out fairly accurately how much blood flow a brain is getting by looking at the size of the hole that lets the carotid artery in through the base of the skull. And then we can apply this technique to look at humans, and at extinct hominins. It turns out that humans are even more exceptional when we look at blood flow to the brain: we’re getting double the flow that you’d expect based on brain size alone.

Early hominins however, Australopithecus and early Homo, aren’t very impressive upstairs, many with less blood flow to the brain than modern apes. Looking at the graph it looks like there are really two grades of brain evolution. In the lower grade, which includes early hominins and modern apes, there is a gradual increase over millions of years. (I’m just guessing here that the ancestors of chimps and gorillas millions of years ago were about as brainy as contemporary hominins, but we’d still like to find more fossils.) And then there is a big leap up to a higher grade with early Homo erectus, and a rapid increase after that. It looks like something major changed with the appearance of Homo erectus, either on the supply side – improvements in food supply making brains more affordable – or on the demand side – a greater fitness payoff to a high energy brain – or both.

Grassroots

1.95 – 1.84 million years ago

A perspective on Australopithecus and early Homo, from researchers at my school, the University of Utah.

Tropical grasses and sedges commonly use the C4 pathway for photosynthesis, which evolved from the C3 pathway used by most plants, in response to lower atmospheric carbon dioxide levels. We can trace an isotopic signature in the teeth of animals that eat C4 plants (and animals that eat those animals). From about 3.5 Mya we see evidence of hominins eating more C4 foods: either grasses (maybe including underground parts) or animals that ate grasses. Paranthropus boisei seems to be a particular champion with the C4s. Chimpanzees, even when they live in open woodlands, mostly stick to eating fruits and leaves. By contrast, exploiting grassroots and sedges to varying degrees may be an important component of australopithecine adaptation to the savannah.

Two Million BC

2.04 – 1.94 million years ago

Two million years ago, there were multiple hominin species in Africa. There was Homo habilis, with a larger brain than any australopithecine, but similar body size and long arms. There was also the recently discovered Australopithecus sediba, with brain not especially large, but maybe reorganized in a human direction, and teeth trending human-wards as well.

A. sediba

There were two robust species that we know of, boisei in east Africa and robustus in southern Africa. The robusts had huge premolars and molars, and enormous jaw muscles running through a large zygomatic arch to attach all the way up to the sagittal crest in the middle of the skull. Gorillas have sagittal crests too, but with them it’s about powerful bites from incisors and canines. You, on the other hand, don’t have a sagittal crest. Your temporalis muscle only runs up to your temple.

The robusts are sometimes given their own genus Paranthropus, other times included in Australopithecus. This reflects uncertainty about their relationships. Did robust morphology evolve once, with both boisei and robustus evolving from aethiopicus? Or did it evolve independently several times, with robustus evolving from Australopithecus africanus in southern Africa?

And remarkably, we now know that three different hominin genera were around not just at the same time and but in the same place, hanging around a South African cave system: Paranthropus robustus, plus Australopithecus africanus (an old-timer, with more than a million year past behind her),  plus Homo erectus (a newcomer, with a more than a million year future ahead of her).

A famous movie cut, from 2001: A Space Odyssey, transitions from a bone club, hurled aloft by an australopithecine 2.5 million years ago, to a spacecraft in the year 2001.

Arthur Clarke and Stanley Kubrick, coming up with the plot for the movie/book, were influenced by the popular author Robert Ardrey. In his book African Genesis, Ardrey casts human evolution as a version of the story of Cain and Abel, except in his version the peaceful vegetarians (robust australopithecines) get clobbered by the club-wielding meat-eaters (gracile australopithecines).

We were born of risen apes, not fallen angels, and the apes were armed killers besides. And so what shall we wonder at? Our murders and massacres and missiles, and our irreconcilable regiments?  Or our treaties whatever they may be worth; our symphonies however seldom they may be played; our peaceful acres, however frequently they may be converted into battlefields; our dreams however rarely they may be accomplished. The miracle of man is not how far he has sunk but how magnificently he has risen. We are known among the stars by our poems, not our corpses.

Ardrey, along with Konrad Lorenz and Desmond Morris, was much in vogue in the 1960s: Sam Peckinpah was another movie director influenced by him. The man could turn a phrase. Unfortunately his speculations on evolution and human behavior are probably not of enduring value: he had the misfortune to take up the topic too early to take on board the sociobiological revolution pioneered by William Hamilton, Robert Trivers, and George Williams, and popularized by E. O. Wilson and Richard Dawkins.

Ardrey may not have been off-base in thinking that weaponry and warfare have been an important motive force in human biological and social evolution (more on this later). But where early stone tools are concerned, a different segue, from Oldowan chopper to Cuisnart may be more appropriate.

Recent research argues that early hominins could have dramatically increased available food energy by pounding vegetables and chopping up meat into more digestible pieces. Tool use may have been an early step in our ancestors’ move to high energy diets. Meat-eating began to be important in human evolution around 2.6 million years ago. Somewhat later we see evidence that some hominins have lighter jaws and aren’t chewing as much. So to celebrate this early dietary revolution, here’s a recipe:

Steak Tartare

Place in a food processor fitted with the metal chopping blade:

1 ½ pounds lean beef (tenderloin, top round, or sirloin) cut into ½ inch cubes

Pulse until meat is coarsely ground, 7-10 seconds. Do not over-process. Remove meat to a chilled platter or individual plates and gently form into 6 individual mounds.

[Optional: Make a spoon shaped indentation on top of each mound and crack into each

1 egg yolk.]

Divide and arrange in small piles around each serving:

½ cup minced onions
½ cup minced shallots
½ cup minced fresh parsley
¼ cup minced drained capers
8-12 anchovies (optional)

Serve immediately and pass separately:

Fresh lemon juice
Worcestershire sauce
Dijon mustard
Hot pepper sauce
Freshly ground black pepper
Salt

From The Joy of Cooking 1997

Blood and brains

Humans are brainy animals. One way to show that is by looking at brain size: our species has the biggest brains, in relation to body size, of any animal. But there’s more to it than that. An earlier post covered the work of Susan Herculano-Houzel. She developed a technique for counting the number of neurons in a brain, or part of a brain. Among most mammals, big animals have a lower density of brain neurons, so they aren’t actually as brainy (measured by neuron number) as you’d think just based on their brain size. Primates however break the usual mammalian rule. Big primates have the same neuron density as little guys, so they really are quite brainy. And humans, with really big brains and (following primate rules) a high density of neurons, stand out even among primates as exceptionally brainy.

This work isn’t much help if we are looking at extinct hominins, when all we’ve got is their fossil skulls. But now there’s some interesting recent research with a new take on the subject. Brains need to be supplied with blood. The more energy they use, the more blood flow is needed. We can now figure out fairly accurately how much blood flow a brain is getting by looking at the size of the hole that lets the carotid artery in through the base of the skull. And then we can apply this technique to look at humans, and at extinct hominins. It turns out that humans are even more exceptional when we look at blood flow to the brain: we’re getting double the flow that you’d expect based on brain size alone.

Early hominins however, Australopithecus and early Homo, aren’t very impressive upstairs, many with less blood flow to the brain than modern apes. Looking at the graph it looks like there are really two grades of brain evolution. In the lower grade, which includes early hominins and modern apes, there is a gradual increase over millions of years. (I’m just guessing here that the ancestors of chimps and gorillas millions of years ago were about as brainy as contemporary hominins, but we’d still like to find more fossils.) And then there is a big leap up to a higher grade with early Homo erectus, and a rapid increase after that. It looks like something major changed with the appearance of Homo erectus, either on the supply side – improvements in food supply making brains more affordable – or on the demand side – a greater fitness payoff to a high energy brain – or both.

Grassroots and fisticuffs

1.95 – 1.84 million years ago

A couple of recent perspectives on Australopithecus and early Homo, from researchers at my school, the University of Utah.

Tropical grasses and sedges commonly use the C4 pathway for photosynthesis, which evolved from the C3 pathway used by most plants, in response to lower atmospheric carbon dioxide levels. We can trace an isotopic signature in the teeth of animals that eat C4 plants (and animals that eat those animals). From about 3.5 Mya we see evidence of hominins eating more C4 foods: either grasses (maybe including underground parts) or animals that ate grasses. Paranthropus boisei seems to be a particular champion with the C4s. Chimpanzees, even when they live in open woodlands, mostly stick to eating fruits and leaves. By contrast, exploiting grassroots and sedges to varying degrees may be an important component of australopithecine adaptation to the savannah.

Not only do australopithecines have enlarged back teeth relative to great apes, but they also have smaller canines. Canines are mostly good for fighting, so it’s nice to think that canine reduction is a sign of our ancestors becoming more peaceful. Could be. But it’s possible they just switched fighting styles. David Carrier argues that australopithecine faces are built to withstand punches, starting from the time that australopithecine hands were capable of forming fists. This might go together with high levels of sexual dimorphism – males, the more violent sex, being bigger than females (but early hominin sexual dimorphism is a contentious subject.)

Two Million BC

2.04 – 1.94 million years ago

Two million years ago, there were multiple hominin species in Africa. There was Homo habilis, with a larger brain than any australopithecine, but similar body size and long arms. There was also the recently discovered Australopithecus sediba, with brain not especially large, but maybe reorganized in a human direction, and teeth trending human-wards as well.

A. sediba

There were two robust species that we know of, boisei in east Africa and robustus in southern Africa. The robusts had huge premolars and molars, and enormous jaw muscles running through a large zygomatic arch to attach all the way up to the sagittal crest in the middle of the skull. Gorillas have sagittal crests too, but with them it’s about powerful bites from incisors and canines. You, on the other hand, don’t have a sagittal crest. Your temporalis muscle only runs up to your temple.

The robusts are sometimes given their own genus Paranthropus, other times included in Australopithecus. This reflects uncertainty about their relationships. Did robust morphology evolve once, with both boisei and robustus evolving from aethiopicus? Or did it evolve independently several times, with robustus evolving from Australopithecus africanus in southern Africa?And remarkably, we now know that three different hominin genera were around not just at the same time and but in the same place, hanging around a South African cave system: Paranthropus robustus, plus Australopithecus africanus (an old-timer, with more than a million year past behind her),  plus Homo erectus (a newcomer, with a more than a million year future ahead of her).

And remarkably, we now know that three different hominin genera were around not just at the same time and but in the same place, hanging around a South African cave system: Paranthropus robustus, plus Australopithecus africanus (an old-timer, with more than a million year past behind her),  plus Homo erectus (a newcomer, with a more than a million year future ahead of her).

Your cuisnart, a prehistory

A famous movie cut, from 2001: A Space Odyssey, transitions from a bone club, hurled aloft by an australopithecine 2.5 million years ago, to a spacecraft in the year 2001.

Arthur Clarke and Stanley Kubrick, coming up with the plot for the movie/book, were influenced by the popular author Robert Ardrey. In his book African Genesis, Ardrey casts human evolution as a version of the story of Cain and Abel, except in his version the peaceful vegetarians (robust australopithecines) get clobbered by the club-wielding meat-eaters (gracile australopithecines).

We were born of risen apes, not fallen angels, and the apes were armed killers besides. And so what shall we wonder at? Our murders and massacres and missiles, and our irreconcilable regiments?  Or our treaties whatever they may be worth; our symphonies however seldom they may be played; our peaceful acres, however frequently they may be converted into battlefields; our dreams however rarely they may be accomplished. The miracle of man is not how far he has sunk but how magnificently he has risen. We are known among the stars by our poems, not our corpses.

Ardrey, along with Konrad Lorenz and Desmond Morris, was much in vogue in the 1960s: Sam Peckinpah was another movie director influenced by him. The man could turn a phrase. Unfortunately his speculations on evolution and human behavior are probably not of enduring value: he had the misfortune to take up the topic too early to take on board the sociobiological revolution pioneered by William Hamilton, Robert Trivers, and George Williams, and popularized by E. O. Wilson and Richard Dawkins.

Ardrey may not have been off-base in thinking that weaponry and warfare have been an important motive force in human biological and social evolution (more on this later). But where early stone tools are concerned, a different segue, from Oldowan chopper to Cuisnart may be more appropriate.

Recent research argues that early hominins could have dramatically increased available food energy by pounding vegetables and chopping up meat into more digestible pieces. Tool use may have been an early step in our ancestors’ move to high energy diets. Meat-eating began to be important in human evolution around 2.6 million years ago. Somewhat later we see evidence that some hominins have lighter jaws and aren’t chewing as much. So to celebrate this early dietary revolution, here’s a recipe:

Steak Tartare

Place in a food processor fitted with the metal chopping blade:

1 ½ pounds lean beef (tenderloin, top round, or sirloin) cut into ½ inch cubes

Pulse until meat is coarsely ground, 7-10 seconds. Do not over-process. Remove meat to a chilled platter or individual plates and gently form into 6 individual mounds.

[Optional: Make a spoon shaped indentation on top of each mound and crack into each

1 egg yolk.]

Divide and arrange in small piles around each serving:

½ cup minced onions
½ cup minced shallots
½ cup minced fresh parsley
¼ cup minced drained capers
8-12 anchovies (optional)

Serve immediately and pass separately:

Fresh lemon juice
Worcestershire sauce
Dijon mustard
Hot pepper sauce
Freshly ground black pepper
Salt

From The Joy of Cooking 1997