4.3 The Evolution of the Brain

Thus far, I have given a general evolutionary account of the emergence of

the primate brain from organisms that developed a light/dark sensitivity

area. In order to explain the evolution of the primate visual system in

particular—from which emerged the uniquely human, conscious ability to

scenario visualize—it is necessary to narrow our focus further and trace the

evolution of the brain from our insectivore ancestor of 65 million years

ago (mya), through the primate missing link, to the emergence of Homo

sapiens some 100,000 years ago (ya). This is the case for at least three

reasons.

First, not only does the visual system utilize some 40% of the monkey’s

neocortex and some 15% of the human neocortex but the visual system

makes further connections with other systems of the brain that are important

in memory formation, emotions, planning, and motor control. Thus,

it seems evident that the visual system evolved for important reasons.

Second, the visual systems of the mammals from which primates evolved

most likely were integral to the animal’s survival. Primates ultimately

evolved from archaic insectivores, and the insectivore needs to have acute

vision in order to see in the dark when it feeds (Jerison, 1973, 1997;

Allman, 1977; cf. Barlow, 1994). Third, the size of the brain in relation to

the body of animals, in general, is an indicator of abilities to integrate and

process pieces of sensory information (Roth, 2000; Jerison, 1997; Kaas,

1993; Armstrong & Falk, 1982). As the brain enlarged throughout primate

evolution, the visual system evolved in complexity as well. In fact, as the

brain increased in relative size, I explain this evolution as nothing short

of the move from noncognitive visual processing, through cognitive visual

processing, to conscious cognitive visual processing in terms of scenario

visualization.

It is generally agreed that archaic primates have evolved from an early

insectivore like Purgatorius, a mouse-sized, squirrel-looking mammal that

spent its life on the ground foraging for insects in the evenings during the

Cretaceous period (see the geological time scale in fi gure 4.2). From Purgatorius,

all primates, tarsiers, lorises, and lemurs likely evolved. Although

the exact phylogenic lines are sketchy, early primates known as Aegyptopithecus

and Proconsul that lived during the Oligocene and Miocene epochs,

respectively, likely are direct antecedents of modern human beings (Anapol,

Geological Time Scale

Eras Periods Epochs

Quarternary

Cenozoic

Tertiary

Mesozoic

Paleozoic

Pre-Cambrian

Millions of Years

before the Present

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Cretaceous

Jurassic

Triassic

Permian

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

.01

2

5

24

37

58

65

142

206

248

290

325

360

417

443

495

545

545–4,550

Figure 4.2

The geological time scale

The Evolution of the Visual System and Scenario Visualization 103

German, & Jablonski, 2004; Fleagle, 1999; Mithen, 1996; Martin, 1990;

Relethford, 1994).

Modern human beings are considered members of the species Homo

sapiens. The following is a categorization of our hominin ancestry. Given

the fact that fossilized skeletal remains of our hominin ancestors continually

are being discovered in parts of the world, along with the fact that

paleoclassifi cation primarily occurs through comparisons of morphological

traits, there are debates among scientists about the exact number and

placement of our ancestors in the hominin family tree (or bush). It is most

probably the case that several of the lineages represent lateral relatives,

rather than direct ancestors. For example, it seems that aethiopicus, bosei,

and robustus lived during the same time with rudolfensis, habilis, ergaster,

and erectus, causing some scientists to classify the former three as in the

genus Paranthropus, rather than classifying them all as in the genus Australopithecus.

Simply put, the further back we go, the more likelihood there

is for disagreement concerning hominin classifi cation. So, the following

classifi cation is tentative and debatable but, nonetheless, represents the

latest research as of the time I am writing this book.

Having said this, there is still a way to classify our hominin lineage(s),

noting a few qualifi cations. Humans are members of the species Homo

sapiens. The order Primate contains all prosimians, monkeys, apes, apemen,

and humans; the suborder Anthropoidae contains monkeys, apes,

ape-men, and humans; the superfamily Hominoidea contains apes, apemen,

and humans; the family Homininae contains ape-men and humans;

the subfamily Homininae contains humans; the genus Homo contains

archaic and modern humans, of which there are seven extinct and one

living species we are aware of at this time, namely, Homo habilis, H.

rudolfensis, H. ergaster, H. hiedelbergensis, H. erectus, H. neandertalensis, H.

fl oresiensis, and H. sapiens (modern humans). Some consider habilis to be

an Australopithecine. Under the family Homininae and in the genus Australopithecus

are included seven extinct species: the gracile Australopithecines,

Australopithecus anamensis, A. afarensis, A. africanus, A. garhi; and the robust

Australopithecines, A. aethiopicus, A. bosiei, and A. robustus. Some classify the

robust group as the separate genus Paranthropus. Toumai Sahelanthropus

tchadensis, Samburupithecus kiptalami, Orrorin tugenensis, Ardipithecus

kadabba, Ardipithecus ramidus, and Kenyanthropus platyops have been discovered

and dated but have an even murkier classifi cation than the species

just mentioned (Stringer & Andrews, 2005; Cameron & Groves, 2004;

White, 2003; Brunet et al., 2002; Hartwig, 2002; Kingdon, 2003; Tattersall,

2002; Stringer, 2002; Brown et al., 2004; Leakey et al., 2001; Johanson, 1996; McHenry, 1998; Abitbol, 1995; Johanson & Edgar, 1996; Wolpoff,

1999; Lieberman et al., 1996; Swisher, 1994; Wood, 1994; Mithen, 1996;

Relethford, 1994).

The various hominin species are situated chronologically as follows:

Samburupithecus kiptalami: lived approximately 8.5–7.5 mya

Sahelanthropus tchadensis: 7–6 mya

Orrorin tugenensis: 6–5.8 mya

Ardipithecus kadabba: 5.8–5.3 mya

Ardipithecus ramidus: 4.7–4.4 mya

Australopithecus anamensis: 4.3–3.9 mya

Australopithecus afarensis: 3.9–2.9 mya

Kenyanthropus platyops: 3.5–3.1 mya

Australopithecus africanus: 3.1–2.4 mya

Australopithecus garhi: 2.7–2.4 mya

Australopithecus/Paranthropus aethiopicus: 2.7–2.3 mya

Australopithecus rudolfensis: 2.6–1.8 mya

Australopithecus/Paranthropus bosiei: 2.4–1.5 mya

Homo habilis: 2.3–1.7 mya

Homo rudolfensis: 2.3–1.9 mya

Australopithecus/Paranthropus robustus: 2–1.4 mya

Homo ergaster: 2–1.5 mya

Homo heidelbergensis: 1 mya–220,000 ya

Homo erectus: 800,000–100,000 ya

Homo neandertalensis: 370,000–80,000 ya

Homo fl oresiensis: 100,000–20,000 ya

Homo sapiens: 120,000 ya–present.

Again, we must keep in mind that it is most probably the case that several

of the lineages represent lateral relatives rather than direct ancestors of

Homo sapiens. The lineage leading to Homo sapiens is what is most signifi -

cant for my project and, as of this time, can be traced as follows: Ardipithecus

kadabba →Australopithecus anamensis →Australopithecus afarensis →

Homo habilis →Homo ergaster →Homo heidelbergensis →Homo sapiens.

Interestingly enough, the earlier hominin species had brains that more

closely resemble the size of a chimpanzee’s brain, while the later species,

like Homo erectus, had brains that were almost as big as ours. Brain sizes

can be estimated from the internal volume of skulls. Typical modern adult

humans have brains that are between 1,200 and 1,400 cm in volume. The

Australopithecines all had a brain around 450 cm in volume. The Homo line

shows a steady increase in size, with Homo habilis having a brain volume

The Evolution of the Visual System and Scenario Visualization 105

of around 700 cm, Homo ergaster having a brain volume of around 900 cm,

and Homo heidelbergensis achieving the 1,200 cm status.

The brains of Homo neandertalensis actually got bigger than ours, but this

is argued to be the result of a larger body mass (see Stringer & Andrews,

2005; Cameron & Groves, 2004; Roth, 2000). Not only did the neandertals

die out but they also left no advanced signs of culture like that of ours,

even though their brains were larger than ours (Mithen, 1996). This is

puzzling. However, we must remember that brain size alone does not

account for intellectual complexity or capacity to solve novel problems

in environments. What accounts for such complexity and/or capacity has

to do with the total number of synaptic connections, as well as the hierarchical

organization of processes and systems in the brain. We can think

of it another way. Elephants and blue whales have larger brains than

humans because of their body mass, but this does not mean that they are

more intelligent. Why? Because they do not have as many synaptic connections

and the more advanced hierarchical arrangement of processes

and systems that we do (see Aboitiz, 1996; Kappelman, 1996). To use a

computer metaphor, it is not just bigger hardware that enables complex

functioning; it is the amount of wiring in the hardware, and how that

wiring is all hooked up, that makes the determination (see Jackendoff,

1987, 1992, 1994; Copeland, 1993; Sternberg, 2001).

Thus far, I have given a general evolutionary account of the emergence of

the primate brain from organisms that developed a light/dark sensitivity

area. In order to explain the evolution of the primate visual system in

particular—from which emerged the uniquely human, conscious ability to

scenario visualize—it is necessary to narrow our focus further and trace the

evolution of the brain from our insectivore ancestor of 65 million years

ago (mya), through the primate missing link, to the emergence of Homo

sapiens some 100,000 years ago (ya). This is the case for at least three

reasons.

First, not only does the visual system utilize some 40% of the monkey’s

neocortex and some 15% of the human neocortex but the visual system

makes further connections with other systems of the brain that are important

in memory formation, emotions, planning, and motor control. Thus,

it seems evident that the visual system evolved for important reasons.

Second, the visual systems of the mammals from which primates evolved

most likely were integral to the animal’s survival. Primates ultimately

evolved from archaic insectivores, and the insectivore needs to have acute

vision in order to see in the dark when it feeds (Jerison, 1973, 1997;

Allman, 1977; cf. Barlow, 1994). Third, the size of the brain in relation to

the body of animals, in general, is an indicator of abilities to integrate and

process pieces of sensory information (Roth, 2000; Jerison, 1997; Kaas,

1993; Armstrong & Falk, 1982). As the brain enlarged throughout primate

evolution, the visual system evolved in complexity as well. In fact, as the

brain increased in relative size, I explain this evolution as nothing short

of the move from noncognitive visual processing, through cognitive visual

processing, to conscious cognitive visual processing in terms of scenario

visualization.

It is generally agreed that archaic primates have evolved from an early

insectivore like Purgatorius, a mouse-sized, squirrel-looking mammal that

spent its life on the ground foraging for insects in the evenings during the

Cretaceous period (see the geological time scale in fi gure 4.2). From Purgatorius,

all primates, tarsiers, lorises, and lemurs likely evolved. Although

the exact phylogenic lines are sketchy, early primates known as Aegyptopithecus

and Proconsul that lived during the Oligocene and Miocene epochs,

respectively, likely are direct antecedents of modern human beings (Anapol,

Geological Time Scale

Eras Periods Epochs

Quarternary

Cenozoic

Tertiary

Mesozoic

Paleozoic

Pre-Cambrian

Millions of Years

before the Present

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Cretaceous

Jurassic

Triassic

Permian

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

.01

2

5

24

37

58

65

142

206

248

290

325

360

417

443

495

545

545–4,550

Figure 4.2

The geological time scale

The Evolution of the Visual System and Scenario Visualization 103

German, & Jablonski, 2004; Fleagle, 1999; Mithen, 1996; Martin, 1990;

Relethford, 1994).

Modern human beings are considered members of the species Homo

sapiens. The following is a categorization of our hominin ancestry. Given

the fact that fossilized skeletal remains of our hominin ancestors continually

are being discovered in parts of the world, along with the fact that

paleoclassifi cation primarily occurs through comparisons of morphological

traits, there are debates among scientists about the exact number and

placement of our ancestors in the hominin family tree (or bush). It is most

probably the case that several of the lineages represent lateral relatives,

rather than direct ancestors. For example, it seems that aethiopicus, bosei,

and robustus lived during the same time with rudolfensis, habilis, ergaster,

and erectus, causing some scientists to classify the former three as in the

genus Paranthropus, rather than classifying them all as in the genus Australopithecus.

Simply put, the further back we go, the more likelihood there

is for disagreement concerning hominin classifi cation. So, the following

classifi cation is tentative and debatable but, nonetheless, represents the

latest research as of the time I am writing this book.

Having said this, there is still a way to classify our hominin lineage(s),

noting a few qualifi cations. Humans are members of the species Homo

sapiens. The order Primate contains all prosimians, monkeys, apes, apemen,

and humans; the suborder Anthropoidae contains monkeys, apes,

ape-men, and humans; the superfamily Hominoidea contains apes, apemen,

and humans; the family Homininae contains ape-men and humans;

the subfamily Homininae contains humans; the genus Homo contains

archaic and modern humans, of which there are seven extinct and one

living species we are aware of at this time, namely, Homo habilis, H.

rudolfensis, H. ergaster, H. hiedelbergensis, H. erectus, H. neandertalensis, H.

fl oresiensis, and H. sapiens (modern humans). Some consider habilis to be

an Australopithecine. Under the family Homininae and in the genus Australopithecus

are included seven extinct species: the gracile Australopithecines,

Australopithecus anamensis, A. afarensis, A. africanus, A. garhi; and the robust

Australopithecines, A. aethiopicus, A. bosiei, and A. robustus. Some classify the

robust group as the separate genus Paranthropus. Toumai Sahelanthropus

tchadensis, Samburupithecus kiptalami, Orrorin tugenensis, Ardipithecus

kadabba, Ardipithecus ramidus, and Kenyanthropus platyops have been discovered

and dated but have an even murkier classifi cation than the species

just mentioned (Stringer & Andrews, 2005; Cameron & Groves, 2004;

White, 2003; Brunet et al., 2002; Hartwig, 2002; Kingdon, 2003; Tattersall,

2002; Stringer, 2002; Brown et al., 2004; Leakey et al., 2001; Johanson, 1996; McHenry, 1998; Abitbol, 1995; Johanson & Edgar, 1996; Wolpoff,

1999; Lieberman et al., 1996; Swisher, 1994; Wood, 1994; Mithen, 1996;

Relethford, 1994).

The various hominin species are situated chronologically as follows:

Samburupithecus kiptalami: lived approximately 8.5–7.5 mya

Sahelanthropus tchadensis: 7–6 mya

Orrorin tugenensis: 6–5.8 mya

Ardipithecus kadabba: 5.8–5.3 mya

Ardipithecus ramidus: 4.7–4.4 mya

Australopithecus anamensis: 4.3–3.9 mya

Australopithecus afarensis: 3.9–2.9 mya

Kenyanthropus platyops: 3.5–3.1 mya

Australopithecus africanus: 3.1–2.4 mya

Australopithecus garhi: 2.7–2.4 mya

Australopithecus/Paranthropus aethiopicus: 2.7–2.3 mya

Australopithecus rudolfensis: 2.6–1.8 mya

Australopithecus/Paranthropus bosiei: 2.4–1.5 mya

Homo habilis: 2.3–1.7 mya

Homo rudolfensis: 2.3–1.9 mya

Australopithecus/Paranthropus robustus: 2–1.4 mya

Homo ergaster: 2–1.5 mya

Homo heidelbergensis: 1 mya–220,000 ya

Homo erectus: 800,000–100,000 ya

Homo neandertalensis: 370,000–80,000 ya

Homo fl oresiensis: 100,000–20,000 ya

Homo sapiens: 120,000 ya–present.

Again, we must keep in mind that it is most probably the case that several

of the lineages represent lateral relatives rather than direct ancestors of

Homo sapiens. The lineage leading to Homo sapiens is what is most signifi -

cant for my project and, as of this time, can be traced as follows: Ardipithecus

kadabba →Australopithecus anamensis →Australopithecus afarensis →

Homo habilis →Homo ergaster →Homo heidelbergensis →Homo sapiens.

Interestingly enough, the earlier hominin species had brains that more

closely resemble the size of a chimpanzee’s brain, while the later species,

like Homo erectus, had brains that were almost as big as ours. Brain sizes

can be estimated from the internal volume of skulls. Typical modern adult

humans have brains that are between 1,200 and 1,400 cm in volume. The

Australopithecines all had a brain around 450 cm in volume. The Homo line

shows a steady increase in size, with Homo habilis having a brain volume

The Evolution of the Visual System and Scenario Visualization 105

of around 700 cm, Homo ergaster having a brain volume of around 900 cm,

and Homo heidelbergensis achieving the 1,200 cm status.

The brains of Homo neandertalensis actually got bigger than ours, but this

is argued to be the result of a larger body mass (see Stringer & Andrews,

2005; Cameron & Groves, 2004; Roth, 2000). Not only did the neandertals

die out but they also left no advanced signs of culture like that of ours,

even though their brains were larger than ours (Mithen, 1996). This is

puzzling. However, we must remember that brain size alone does not

account for intellectual complexity or capacity to solve novel problems

in environments. What accounts for such complexity and/or capacity has

to do with the total number of synaptic connections, as well as the hierarchical

organization of processes and systems in the brain. We can think

of it another way. Elephants and blue whales have larger brains than

humans because of their body mass, but this does not mean that they are

more intelligent. Why? Because they do not have as many synaptic connections

and the more advanced hierarchical arrangement of processes

and systems that we do (see Aboitiz, 1996; Kappelman, 1996). To use a

computer metaphor, it is not just bigger hardware that enables complex

functioning; it is the amount of wiring in the hardware, and how that

wiring is all hooked up, that makes the determination (see Jackendoff,

1987, 1992, 1994; Copeland, 1993; Sternberg, 2001).