TO THE AGE OF THROWERS
By Richard W. Young
If you are interested in human origins and evolution, you have a
treat in store for you in what follows--Eduard Kirschmann’s unusually creative
and provocative new book, available for the first time in English, thanks to
Susan Way’s lucid translation from the German.
The queries, “where did we come from?” and “what made us the way we
are?” represent two of the most profound questions that seem to haunt the human
mind. All cultures have developed myths
and beliefs that seek to provide the answers.
These myriad tales, so varied in their style and content, that seek to
account for our origins and characteristics, reveal the range and creativity of
the unfettered human mind. With the development of science, a new way of
answering questions about human origins became possible–a fettered or disciplined
method of thinking in which ideas and explanations are constrained by what can
be observed, recorded and measured. By
the 19th century there was sufficient evidence to support the
conclusion that plants and animals had evolved from earlier forms
(rather than being the result of a single act of creation). In 1859 Charles Darwin described the mechanism
by which this occurs and in 1871 he presented his argument that humans had
evolved by this same process. Today
biological scientists universally agree that “nothing makes sense in biology
except in the light of evolution”.
Eduard Kirschmann’s seminal work, The Age of Throwers, is
thoroughly Darwinian and remarkably original.
It supplies a fresh new way of thinking about human origins and human
evolution that provides explanations for several of the most significant
features of our species.
The Throwing Hypothesis. Kirschmann begins with a plausible and stunningly
simple assertion: the human lineage began when a
population of chimpanzee-like apes began to
throw stones more frequently to ward off
predators. It is an assertion that is certainly
reasonable, when we consider that throwing is a natural human behavior. Children do it without training or
encouragement. Adults are inclined to
throw objects in self defense or with aggressive purposes. We pay enormous salaries to professional
throwers so we can watch them perform.
Human aimed throwing is an exceedingly complicated act, involving the
entire body under exquisite control by the brain and no other animal can do
it. We are unique in this
regard. We are the greatest throwers of
all time! Considering these
observations, it seems clear that human throwing had a long evolutionary
history that profoundly affected our brain and body. This is the Throwing
Hypothesis, defined by Kirschmann as “the assumption that very demanding and
extensive adaptations to aimed throwing occurred during the course of hominid
evolution” (Chapter 1.4). If true, our ancestors must have depended
importantly on this behavior for survival and success in leaving
descendants. Nevertheless, the
origins of human throwing prowess have never
received an evolutionary explanation. This is a
gap in our understanding of major
proportions. Herein lies a
measure of the magnitude of what Kirschmann has accomplished in this book. Not only does he provide such an explanation,
he makes throwing the basis of a new theory of human evolution. It is an
ambitious and refreshingly original attempt to explain how we began, and how we
came to be the way we are.
The Throwing Hypothesis is the Core Principle of a Theory. According to Lewin (1997),
any theory of human evolution must explain how it was that an apelike ancestor,
equipped with powerful jaws and long, daggerlike canine teeth and able to run
at speed on four limbs, became transformed into a slow, bipedal animal whose
natural means of defense were at best puny.
Add to this the power of intellect, speech, and morality and one has the
complete challenge to evolutionary theory.
This book meets this challenge.
It provides new insights and stimulating answers to all these questions.
Kirschmann does not assert that he is presenting a theory. He speaks of a “model” that is based on his
throwing hypothesis. Nevertheless, his
proposal has both the structure and function of a theory, and thus–call it what
you will–it meets the definition of a theory.
Theories are explanatory structures.
As Nagel (1961) emphasized, it is the desire for explanations
controlled by factual evidence that
generates science; and it is the organization of knowledge based on explanatory
principles that is the distinctive goal of science. A theory offers a systematic account of
widely diverse phenomena. It is the most
inclusive of scientific explanatory structures.
Founded on a small number of principles that explain a large number of
empirical laws--regularities that emerge from analysis of observations–a theory
is more elegant when it has a minimum of clearly defined principles and can
account for a large body of information.
The aim is simplicity in structure and enormity in scope. Theories explain regularities and provide a
deeper and more accurate understanding of phenomena by showing that they are
instances of general rules which are manifestations of the underlying
principles (Goudge, 1961; Hempel, 1966; Nagel, 1961).
Darwin’s theory is a classic example. His basic principles–variation and natural
selection–are parsimonious and the scope of their application encompasses all
of biology. (A theory of human
evolution is but a tiny subdivision of Darwin’s grand theory, but it is of
special importance because it concerns our species!) From this perspective, theories are the
highest goal of science. Those who denigrate them as too speculative
(“Darwinian evolution is just speculation; it’s only a theory”) overlook that a
proper scientific theory can be tested by evidence and thereby strengthened or
weakened–and even falsified.
In my judgement, Kirschmann’s
Age of Throwers is the best theory of human evolution since Darwin’s
1871 classic. This may sound
extravagant, but it can be justified.
First, how does Kirschmann’s theory rank in comparison to existing theories
of evolution? Astonishingly, there
are none! There has not been one
since the synthesis of genetics and Darwinism took place over 50 years
ago. In the modern era, despite a
substantial increase in the volume of evidence in all related fields of science,
only a collection of isolated “hypotheses” concerning restricted aspects of
human evolution has emerged. Thus, we
have a killer ape hypothesis, a hunting hypothesis, a scavenging hypothesis, a
gathering hypothesis, a cooking hypothesis, a food-sharing hypothesis, a
nuclear-family hypothesis, numerous bipedalism hypotheses, hypotheses to
account for human sexuality, coalition enforcement, the enlarged brain and
aspects of modern morality and mentality.
One of these, the killer ape hypothesis, has been classified as a “myth”
(de Waal, 2001); another, the hunting hypothesis, has been branded as a fable
(Cartmill, 1993). None has garnered
widespread support. (According to Cartmill,
even Darwin’s 1871 classic was only nominally “Darwinian”, since it did not
represent human traits as adaptations to anything!)
In the absence of a comprehensive modern theory of human evolution,
Kirschmann’s book is an anthropological landmark. It is founded upon a single
principle (“the throwing hypothesis”), is explicitly Darwinian, and extensive
in scope. It derives its explanatory
power from adaptation to a behavior that is oddly missing from any of the
hypotheses cited above. Kirschmann asserts
that the human lineage began with a throwing specialization. As he phrases it, “the weapon characteristic
was transferred from the teeth to the hands at the beginning of hominid
evolution” (Chapter 3.3.2). This
approach gains credibility because the basic postulate--that humans are
specialized throwers--is supported by evidence commonly available to every
one of us. Kirschmann explains how we
gained this unprecedented prowess and shows how this behavior can help account
for many of our other unique features.
Darwin’s View: 1871. Some of the ideas developed by Kirschmann can
be traced back to the great man himself.
In Darwin‘s 1871 treatise, he sought primarily to demonstrate the
probability that humans had evolved by the same process of evolution he
had described for other living species. A detailed narrative of how
humans evolved was not possible.
Existing knowledge of the cause of variation and the nature of the
hereditary process was essentially nil and evidence of fossil hominids too
scanty to be useful. Nevertheless, his
brilliant mind provided hints, intimations and ideas of how certain human
traits might have arisen. Among these was the suggestion of a linkage between
throwing, weapons, the structure of the hand and bipedalism, a concept which
Kirschmann expands and elaborates. Here
is what Darwin said: In throwing a stone
or spear a man must stand firmly on his feet (p. 138). Ape hands are good for climbing trees but are
less perfectly adapted for diversified uses.
The hands and arms could hardly have been come perfect enough to have
manufactured weapons, or to have hurled stones and spears with true aim as long
as they were used for locomotion or climbing trees. From these causes alone it
would have been an advantage to man to have become a biped (p. 141). They would thus have been better able to have
defended themselves with stones or clubs, or have attacked their prey, or
otherwise obtained food. The best
constructed individuals would in the long run have succeeded best, and have
survived in larger numbers (p. 142). As
they acquired the habit of using weapons, they would have used their jaws and
teeth less, and these would have become smaller (p. 144).
A few pages later (pp. 155-156) Darwin refers to the Duke of
Argyll’s criticism that the human body has diverged from the structure of
“brutes” in the direction of greater physical helplessness and weakness, which
seems impossible to ascribe to natural selection. He adduces the naked and unprotected state of
the body, the absence of great teeth or claws for defense, the lack of physical
strength, the slow speed in running, the slight sense of smell by which to
discover food or avoid danger and the reduced ability of quickly climbing trees
to escape from enemies. It does sound
like a recipe for extinction. How does
Surprisingly, he says nothing about throwing stones and spears or
swinging clubs! Instead, he plays the
“intelligence” card: The slight
corporeal strength, his little speed, his want of natural weapons &c., are
more than counterbalanced, firstly by his intellectual powers, through
which he has whilst still remaining in a barbarous state formed for himself
weapons, tools, &c., and secondly by his social qualities which lead
him to give aid to his fellow-men and to receive it in return. The earliest progenitors of men were no doubt
inferior in intellect and social disposition, but they might have existed or
even flourished, if, whilst they gradually lost their brute-like powers, such
as climbing trees &c., they at the same time advanced in intellect
Thus, a connection between throwing, weapons, the hand and
bipedalism can be traced to Darwin, but he did not develop the concept, and
when it seems he could have used it, he chose not to do so. Now, 131 years later, Kirschmann answers
the Duke of Argyll’s protestation by playing the “throwing” card.
Modern Darwinism. In current
perspective it is behavior that drives evolutionary change when it
affects reproductive success. Heritable variations are irrelevant to evolution
if they are not reproduced. A satisfactory theory of evolution must identify an
innovative behavior which caused the earliest hominids to branch off from the
ancestral apes because it yielded reproductive advantages. Furthermore, these
benefits must persist for a prolonged period during which adaptation to the new
behavior can occur. The initial behavioral change and each subsequent stage in
its improvement must provide reproductive advantages for adaptation to
continue. This requirement was a serious
problem when bipedalism was thought to be the inaugural hominid behavior. It
proved an insurmountable obstacle to show how bipedalism would lead to
increased reproductive success during the millions of years of body remodelling
required to bring upright gait to its current (still unimpressive) levels of
Aimed throwing of rocks avoids this impasse. On the reasonable assumption that this
behavior would give apes who used it an immediate advantage in reproductive
competition with conspecifics who did not–by increasing their survival, access
to food, defense against predators, opportunities to breed, etc.–we can readily
see that this advantage would be open-ended.
In each generation thereafter, those who were the most effective rock
throwers would continue to have a reproductive advantage. As long as this advantage was maintained, any
heritable variation that enhanced the behavior would tend to be selected. This is essentially the process envisioned by
Kirschmann. During adaptation to aimed
throwing, variations were selected that improved this behavior when they
yielded a net reproductive advantage.
This led to augmented throwing proficiency and gradually brought about a
redesigned body and a more capable brain.
Highlights of “The Age of Throwers”.
Kirschmann proposes that several million years ago, some chimpanzee-like apes
initiated the hominid lineage when males began to throw rocks at predators for
self defense. Reduced predation was the
main advantage gained by the earliest stone-throwers. Hominid males carried rocks wherever they
went. It was their “master tool”. When thrown it was a weapon. It was a useful hammerstone for cracking
bones so the marrow could be eaten. It
was a nutcracker. It could be thrown
against a boulder to get sharp-edged fragments for cutting. (Eventually it would be struck against
another rock to obtain sharp edges in a way that didn’t ruin its other
functions). Hominids gradually gained
the upper hand in their competition with predators due to their increasing
adaptation to rock-throwing. When, due
to millions of years of abuse, predators became wary of the hominids late in
the Australopithecine stage, hominids started chasing them from their kills and
eating what was left of the carcasses.
This was followed by the era of Homo erectus, the peak period of
the Age of Throwers. With the predator
problem now overcome, the hominid population was free to expand. This led to conditions in which males in
rival groups competing for scarce resources began to throw rocks at each
other. This, in turn, resulted in
changes in skull shape and increased skeletal robusticity which reduced the
incidence of fractured bones from rock projectiles. By this stage, adaptation of the skeleton to
throwing was largely completed, but further fine-tuning of throwing mechanisms
in the brain may have continued.
The proposal that the throwing adaptation had a profound effect on
the evolution of brain is among the most exciting and potentially fertile of
Kirschmann’s many creative ideas. He
also shows that an adaptation to throwing behavior can account for several
additional human characteristics that have until now lacked a compelling
evolutionary explanation, including bipedalism and the structure of the
hand. These are weighty issues, and
Kirschmann has tied them together in a provocative new way. Here are a few
The Hominid Ancestor. Any theory of
human origins must have a starting point–the ancestor from which the hominid
line began. In chapter 2
Kirschmann examines this topic. He
chooses for the hominid ancestor our nearest relative, Pan troglodytes,
the common chimpanzee. The habitat of
chimpanzees resembles that in which the earliest hominids are believed to have
lived and many aspects of their behavior remind us of ourselves. The most
ancient hominid fossils strikingly resemble chimpanzees. More is known about the anatomical structure
and behavior of chimpanzees than of any non-human primate. Thus, this species
provides an extensive data base of objective scientific evidence with which to
begin. Humans, according to Kirschmann, can be thought of as “chimpanzees that
have become optimized for throwing” (1.4).
His account begins when the ancestral apes advanced from a habitat
on the edge of the savannah into a drier zone. Climatic changes that caused
their woodland habitat to shrink may have played a role in this migration (3.3.2).
On the grasslands they responded to the increased danger of predation by using
sticks and stones to defend themselves (1.4). This resembles chimpanzee
behavior and thus follows naturally from the chimpanzee model. Hand-to-hand
fighting is risky. The Australopithecine may have used sticks as clubs, but
stone projectiles had clear advantages as distance weapons (3.2).
Genetic Advantages of Throwing. In
open country, when our ancestors found themselves in dangerous situations,
weapons took on increased importance for their fitness (3.3.2)--that is,
for their genetic reproductive success (2.2). Evolution is an
integrative process in which all the advantages and disadvantages of a
variation for the fitness of the bearer undergo simultaneous consideration (3.1).
Throwing adaptations only make sense for evolutionary considerations if this
activity had a consistent, high importance for the reproductive success of the
hominids. The capacity in the use of weapons should, therefore, have exercised
enormous influence on their fitness (3.4). In addition to the advantages resulting from
predator defense, successful
reproduction often means prevailing over members of one’s own species
and especially one’s own sex (4.3).
In chimpanzees, and presumably early hominids, rank order among men had
a strong influence on reproductive success (5.4). Marked sexual selection in a multi-male
society was the most important factor in the evolution of humans. Through sexual selection the most imposing males
were preferred by females. The best throwers belonged to the most imposing
males of the group, with correspondingly good prospects of high rank and above
average reproductive success. Intellectual abilities developed because of
throwing adaptations also had a direct high importance for rank and thus for
reproductive success (6.6). I
have suggested elsewhere some possible additional routes to reproductive
success from effective throwing and clubbing (Young, 2002a). Adding these to the list strengthens
Bipedalism. One of the great enigmas
of human evolution is the question of why our ancestors broke from the
mammalian pattern and began walking on their hind legs. What conceivable advantage could they have
gained by doing that? Kirschmann offers
a new and fascinating explanation: upright gait was linked to upright
An important reason must have existed for the development of
bipedalism. Specialization for the use
of weapons has the potential to be such a reason (3.2). Throwing for
defense against predators is viewed as sufficient explanation for the
transition to walking upright (3.6), but this isn’t the only
reason. The transport of stones for
defensive weapons also required upright locomotion (1.4). Furthermore, as the throwing adaptation led
to increased mobility of the wrist, this would have hindered the use of hands
in walking. Upright orientation of the
upper body for throwing could have also been one of the causes of adopting a
vertical gait. “My interpretation of the
transition to bipedality”, he writes, “thus rests upon multiple advantages of
walking upright for the application of weapons” (3.3.2).
The Human Hand. 19th
century scientists were awed by the perfection of the human hand. Some thought it so perfect it stood as
evidence of a supernatural designer. Yet
none of the authorities on human evolution since then–not Keith, not Elliott,
not Dart, nor anyone after them–has developed a compelling explanation for the
unique structure of the human hand.
(Recently it has been suggested that the later stages of hand evolution
may have been influenced by stone tool-making).
All previous hypotheses to explain bipedalism are mute about the
evolution of the hand. This seems odd,
because “hominids became bipedal in order to free the hands” is a classic
anthropological dictum (Pilbeam, 1970; Landau, 1991). Since tottering on two feet would seem to
offer disadvantages, the hands must have been doing something extremely
valuable to compensate for the reduced balance, speed and endurance that
accompanied bipedalism. What the hands were doing seems to be crucial to
understanding why hominids became bipedalists, and the structure of the human
hand should provide clues about that behavior.
Indeed, if Kirschmann is right, the human hand should be adapted for
Kirschmann’s breakthrough idea identifies the causal factor in the
development of bipedalism, connects it with a behavior involving the hands, and
relates that to hand structure.
Bipedalism evolved because of the reproductive benefits of throwing,
and it was adaptation to this behavior that led to modifications that produced
our “perfect” hands. The precision of
the grip and the sensitivity of the fingers are critical to throwing. Both are associated with the large areas of
the motor and sensory cortex in which the hand is represented (1.4; 3.3.1).
The long, opposable thumb is essential for the throwing grip (3.1). I believe Kirschmann is right–but only
half-right–in attributing human hand structure to a throwing adaptation. There
are two unique human grips, identified by John Napier (1956), who called
them the “precision grip” and the “power grip”.
I have presented evidence that the precision grip is a throwing grip but
the power grip is a clubbing grip (Young, 2002b). This suggests that our ancient ancestors were
throwing and clubbing.
Handedness is also a uniquely human
trait (ninety percent of us are right-handed).
This ancient hominid trait has not yet received a satisfactory evolutionary
explanation (Young, 2002a). Once again, the throwing hypothesis provides an
insight. Kirschmann relates handedness to the rotation of the upper body around
its long axis in the throwing motion. Because the earliest stone tools seem to
have been made predominantly by right-handed stone-knappers 2.5 million years
ago, Kirschmann concludes that by then hominids were capable of rotating the
upper body in this manner and had integrated it into the acceleration procedure
of the throwing motion (3.3.2; 7).
Evolution of the Human Brain. Few issues in paleoanthropology excite
greater interest than the remarkable increase in size and capability of the
human brain during human evolution.
Kirschmann’s analysis makes it seem likely that throwing was
involved, and in proposing this novel approach he opens a new research domain.
This is certainly one of the major accomplishments of his book. With increasing adaptation to aimed throwing,
not only did decisive changes take place in the human body plan, the brain entered
new realms of achievement (1.4). He argues convincingly that the act of
aimed throwing is extremely complex, and most of the complexity is lodged in
the brain. He gives a provocative
glimpse into the wonders in store for researchers who begin to isolate the
underlying brain networks and processes that make possible the astonishing feat
of long-distance, accurate, targeted throwing of high-speed missiles.
The human throwing motion entails an unusually effective coiling and
uncoiling of the body that begins in the legs and feet, then travels through
the hips, torso, shoulder, upper arm, lower arm, wrist and fingers, generating
a cumulative packet of kinetic energy that is transferred to the missile, which
must be released at a precisely controlled instant to attain an accurate
trajectory toward the target (Young, 2002a).
Kirschmann characterizes it as consisting of six different rotations
plus the release, combined in an intricately coordinated movement that is ballistic
(1.4). A regulated motion
can be controlled as it takes place, but a ballistic motion is completed
too quickly for any regulation to occur. This puts throwing in a very special
category of human behavior. All the variables affecting the throw have to be
worked out in advance and inserted into an action protocol (3.3.1).
The capacity to perform this unusual, coordinated, exceedingly
rapid, sequential series of movements is part of the normal developmental
sequence. It is more advanced in boys
(Gesell, et al.1940) and in men compared to women, as predicted by Kirschmann’s
assessment that this and certain other sexually dimorphic traits can be
explained by attributing them to the specialization of men for throwing in the
course of evolution (3.3.1). Possibly no greater feat of coordination than
the human throwing motion has ever evolved, and it must have involved highly
significant modifications of the brain (3.3.1). Beginning with analysis
of sensory information that precedes the throw, Kirschmann emphasizes the
importance of calculating target distance (1.4). He believes that
distance calculation for accurate throwing was a major force in remodelling
brain structure and causing brain expansion. Cognitive performance evolved as a
solution to one task can easily be applied to other tasks (1.4). The
highly developed human ability to construct complex scenarios originally stood
in the service of evaluating distances (3.3.4; 6.8; 7). This, combined with the evolved thrower’s
abilities to manipulate sequential data, may underlie human ability for
advanced planning and play a role in the development of language (7).
In his analysis of determining target distance,
Kirschmann discusses the mechanisms by which the human brain reconstructs the
third dimension from a two-dimensional retinal image and concludes that only
the known size of observed objects offers a basis for calculating absolute
distances beyond 3 meters. Distance is determined from a comparison of the
(remembered) size of objects with the size of the visual angle (the dimensions
of the object’s image on the retina) (3.3.4). This means that the ability of the human
brain to perceive distances is significantly dependent upon memory.
This, in turn, contributes importantly to the high level of human recognition
abilities. Objects first must be identified, then
estimates of size and shape can be called up from memory. These brain
mechanisms are all part of the throwing adaptation.
Evaluating the distance to a target (which may be moving
in any direction), calculating the required trajectory of the missile to reach
the target and intercept it if it is moving, deciding what to throw and when to
throw it based on previous experience, activating the throwing-motion
action-protocol after adjusting it according to analysis of sensory input,
coordinating the contractions of all the involved muscle groups to generate
maximum kinetic energy, and timing the release of the missile precisely–all
these are unique abilities that developed during human evolution. They support Kirschmann’s assertion that
cognitive capacity evolved as part of the throwing adaptation should be
accorded great significance (3.3.1).
Kirschmann maintains that adaptation to throwing is sufficient to
explain the growth of the brain in Australopithecus and its subsequent
expansion in Homo habilis (7). The increase in brain volume at
least through early Homo erectus is mainly due to specializations for
targeted throwing (6.1). The transition to H. erectus, when life
in the trees was abandoned, marks the conclusion of physical adaptations to
throwing (4.3). When, at this time, hominids began to throw at each
other, the estimation of large distances gained new importance driving an
additional expansion of brain performance (4.1; 7). Further
encephalization in subsequent hominids, on the other hand, can be attributed
mainly to selection for language and raised requirements on the brain of social
behavior within groups (4.3; 7).
Beyond the Throwing Hypothesis.
Towards the end of this thought-provoking book, in Chapters 5 and 6, Kirschmann explicitly
ventures beyond the scope of the “pure” thrower hypothesis and grapples with
several additional issues for human evolution, such as why we fall in love,
human reproductive strategies and male homosexuality. (Even here he points out possible connections
between throwing rocks and human sexual features such as reduced testicular
size, loss of the penis bone, and the development of protuberant female
breasts). He then takes up the question
of cultural evolution (including speech and morality) (6.5). Cultural
information, he points out, is not selected to optimize the reproductive
success of single individuals, and it is stored and transmitted differently
than genetic information. Cultural features can develop a life of their own, and
become distant from reality. (The scientific method provides a remedy). Even
when he goes beyond the limits of his core principle, he always seems to have
something new and provocative to say about each issue he examines, and even
when his explanations may not be totally compelling, they are always
Predictions. In an unusual and bold departure from most
attempts to explain features of human evolution, Kirschmann offers several
predictions based on his model. You will find them in Chapters 3.3.2; 3.3.4;
4.1 and 7.
Conclusion. It seems clear that Kirschmann has identified
something very basic about the manner of our evolution and has opened the door
to a vast new field of scientific research--investigation of the effects of a
throwing adaptation on the human mind and body. His basic theme is plausible,
Darwinian, and consistent with a wide array of evidence. It states that the
hominid lineage began when a group of apes began to throw rocks as weapons in
conflict situations, a behavior which brought such important and sustained
improvement in reproductive success that during subsequent millenia they became
to this behavior. This simple assertion not only accounts for the
unrivaled human proficiency at powerful and accurate throwing, the unique
throwing motion that appears as part of
the developmental sequence, our fascination with the feats of great throwers,
and our natural inclination to throw objects in self defense or anger, it also
offers a route to explaining an impressively long list of other human
characters, including upright stance, bipedal gait, the unprecedented form of
our hands and the expanded size and capacities of our brains. The specialized use of hand-held weapons
provides a simple, elegant perspective for rethinking the classic problems of
human origins and the process of how we came to be the way we are.
Kirschmann remarks that
culture, unlike biology, offers the opportunity for a sudden change of major
importance. In this book he has provided
the basis for a significant advance in our understanding of human evolution.
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