Summary: With the evidence of our unique fitness for fire-making, the picture is complete. Nature is uniquely fit for man, designed with us in mind. The anthropocentric claim of Judeo-Christian tradition is vindicated.

Editor’s note: Biologist Michael Denton’s new book, The Miracle of Man: The Fine-Tuning of Nature for Human Existence, is out now. This essay is adapted from Chapter 11, “The Fire-Makers.”

As I show in my book The Miracle of Man, the path followed by our ancestors from stone tools to our current technological civilization was, in broad outline, the only possible path, and it was a path only possible because of yet another stunning ensemble of prior environmental fitness in nature. Not only was the “chosen path” unique, but only a special type of unique being very close to our own biological design could have taken the first and vital step to technological enlightenment, fire-making.

From first principles, a creature capable of creating and controlling fire must be an aerobic terrestrial air-breathing species, living in an atmosphere enriched in oxygen, supportive of both respiration and combustion. This fire-maker must have something like human intelligence to accomplish the task, and while it is true that other species — e.g., dolphins, parrots, seals, apes, and ravens — possess intelligence and remarkable problem-solving abilities, as far as is known, no other organism comes close to the intelligence of humans. 

The species in question also needs to be mobile and possess high acuity vision in order to be able to create and master fire, and follow the subsequent route via metallurgy to an advanced technology.

Being a social species possessed of language would also have been essential for the peripheral tasks associated with the regular making and controlling of fire among small tribal groups, including the hewing and collecting of the necessary wooden fuels to initiate and sustain the fire. While many other species are social, none possesses a communication system remotely as competent as human language for transmitting information, including abstract concepts.

In addition to being terrestrial, air breathing, sighted, mobile, intelligent, social, and possessed of language, a fire-maker also needs the right anatomy. And in keeping with the anthropocentric claim, only humankind of all the creatures on Earth is properly endowed with the right build to make and control fire. Neither a giraffe, nor an elephant, nor a parrot, nor a cat, nor a chimp nor any other terrestrial organism has the right anatomy to master fire, none apart from humans.

Hands and Arms

As any boy scout or girl scout knows, starting a fire by rubbing two sticks together requires considerable manual dexterity and persistence. And as Tom Hanks’s character found out in the film Castaway, even with the superb manipulative abilities of the human hand, it is difficult to start a fire using traditional frictional methods, such as rubbing two pieces of wood together. However, with practice and using various simple devices such as a fire drill, most humans can master the skills necessary to initiate a fire. 

No other species on Earth possesses an organ remotely as capable as the human hand for initiating and maintaining a fire and for intelligent exploration and manipulation of the natural world. One of the earliest and still most fascinating discussions of this adaptive marvel was given by the first century Greek physician Galen:

To man the only animal that partakes in the Divine intelligence, the Creator has given in lieu of every other natural weapon or organ of defence, that instrument the hand: applicable to every art and occasion…. Let us then scrutinize this member of our body; and enquire, not simply whether it be in itself useful for all the purposes of life, and adapted to an animal endowed with the highest intelligence; but whether its entire structure be not such, that it could not be improved by any conceivable alteration.

Galen then proceeds for several pages to detail the genius of the human hand. At one point he declares, “Whoever admires not the skill and contrivance of Nature, must either be deficient in intellect, or must have some private motive, which withholds him from expressing his admiration. He must be deficient in intellect, if he do not perceive that the human hand possesses all those qualifications which it is desirable it should possess; or if he think that it might have had a form and construction preferable to that which it has.”

The perfection of the hand was a popular topic among 19th-century natural theologians such as Oxford Professor of Medicine John Kidd, who quoted liberally from Galen. Charles Bell, in his Bridgewater Treatise, also waxed lyrical about the hand, while citing one of the ancient Greek thinkers: “Seeing the perfection of the hand, we can hardly be surprised that some philosophers should have entertained the opinion with Anaxagoras, that the superiority of man is owing to his hand…. it is in the human hand that we have the consummation of all perfection as an instrument.”

Only the great apes, our cousins, come close. Yet the hand of the chimp and gorilla, although possessing a partially opposable thumb, is far less adapted to fine motor movement and control than is the human hand with its fully opposable thumb. Although some chimps exhibit a remarkable manual dexterity for certain tasks, none can match the manual dexterity of the human hand. And this is obvious on watching chimps at a “tea party” at the zoo. A dining task we hardly think about proves comically challenging for them due to their limited manual dexterity. 

Science journalist Christopher Joyce reviewed the unique capacities of the human hand in a 2010 article at NPR, drawing on insights from two of his interviewees, anthropologists Erin Marie William and Caley Orr:

Now, apes make tools. Scientists have trained a bonobo, called Kanzi, to do that. But Kanzi’s not much good at it.

“He just can’t get the motions down,” Williams says. That’s because he can’t grip the stones, his thumbs aren’t long enough and his fingers are too long and he’s clumsy. He can’t move his wrists — he can’t extend his wrist and get this important “snap.” He makes a mess.

… Anthropologist Caley Orr… has laid out the skeletal hands of three apes and a human. The apes’ hands are enormous — the orangutan’s is like a catcher’s mitt. But their thumbs are tiny and splayed out to the side; the fingers are long and curved. They look powerful, but Orr says the strength runs vertically, from the wrist up through the fingers. That’s good for hanging on tree limbs, but not for much else.

…. The human hand is smaller, and it works differently. Orr hands me a two-foot-long club to illustrate.

“Here, try to hold this without using your little finger, and just using those other digits,” he says. That’s the way an ape might hold it. I make to swing it but realize it will fly out of my hand if I do.

The strength in my hand extends across my palm. My thumb is stronger, and so is my pinky. I can wrap that thumb over my other fingers and then secure the grip at the bottom with my pinkie. An ape can’t manage that very well.

And my opposed thumb and wider fingertips also mean I can grip a round stone — like a hammerstone — with more control than an ape can.

I have the hand of the ultimate toolmaker.

The hand’s attachment to the end of a highly mobile appendage about two-and-a-half feet long — the human arm — further contributes to its universal utility and enables the hand to manipulate objects some distance from the body, no small advantage when manipulating fire. Moreover, because of the hand’s positioning at the end of the arm, its manipulative activities can be readily observed by our eyes, which are placed forward facing on the head so that the activities of the hand can be readily observed. 

Other primates have arms of sufficient length for manipulating fire, but their arms and hands have another role that handicaps them for the work of adroitly manipulating tools. All the great apes are basically quadrupeds, or more precisely, knuckle-walkers as defined by Richard Owen in the 19th century. Our upright bipedal gait and android design free the human arms and hands from the ambulatory function, allowing them to take on adaptations for delicate activities requiring fine motor control. Among primates, a habitual bipedal posture is only present in humans and in a handful of fossil hominin species. This bipedal posture enabled our arms and hands to acquire their unique manipulative functions, which in turn enabled our ancestors to initiate and control fire, and carry out the peripheral activities associated with fire-making, such as hewing and collecting wood, as well as the activities associated with the subsequent development of metallurgy such as mining for ores and building kilns, not to mention the ability to construct a great diversity of tools and instruments, the use of which has been crucial to the development of technology and advances in scientific knowledge.

The Right Size

Possessing such a superb manipulative organ as the hand and an upright bipedal android form that frees the arms and hands for purely manipulative tasks are not in themselves sufficient. They would be of no avail unless we were the right size. Only an android organism of approximately our dimensions can readily make and control fire. To illustrate, let’s begin very small and then work up. An android organism the size of an ant — like Ant Man in the Marvel comics — would be far too small because the heat would kill him long before he was even several body lengths from the flames. As Hu Berry points out, “Ants cannot use fire, for the simple reason that the smallest, stable fire must be much larger than an ant. Ants cannot therefore carry fuel close enough to a fire to maintain it.”

Even diminutive humans two feet tall, possessed of our android design and all our unique anatomical adaptions, would face enormous difficulties in attempting to manipulate fire. Although the recently discovered species of diminutive humans Homo floresiensis did use fire, it seems likely that a species any smaller than their reported height of 3.5 feet would have considerable difficulty. 

There is another consequence of being smaller. In a fascinating article in the American Scientist entitled “The Size of Man,” author F. W. Went points out that organisms much smaller than humans lack the ability to generate the necessary kinetic forces to procure the essential raw materials for fire making and metallurgy. This is because the kinetic energy generated when a mass moves a particular distance (the head of a hammer striking a nail, an axe hitting a tree trunk, a pick hitting an ore deposit) varies as the length traversed raised to the fourth power (kinetic energy = KL⁴). And this means, as Went explains, that “if we assume that a spear or a club of a size proportionate to body size is handled by a 7 ft giant, its impact would be 4 times greater than when handled by an ordinary 5 ft 8 in. man… But compared with an ordinary man, the blow of a 3-year old child or a 3 ft creature in general could only produce one twenty-fifth of the energy, utterly insufficient to kill prey or hunt larger animals.” Consequently, “a 3-ft man could neither cut lumber nor excavate a mine in solid rock.”

Stephen Jay Gould likewise addressed the issue of bodily size, noting that kinetic energy increases with length raised to several orders of magnitude. He goes on to confess “a special sympathy for the poor dwarfs who suffer under the whip of cruel Alberich in Wagner’s Das Rheingold. At their diminutive size, they haven’t a chance of extracting, with mining picks, the precious minerals that Alberich demands.”

So our size is right for approaching a fire, for generating the necessary kinetic forces to hew the wood needed to fuel high temperatures fires, and for mining metal ores from rocks. We could be neither fire-makers nor metallurgists if we were significantly smaller.

On the other hand, it is fortunate that the ability to hew wood and mine for ores does not necessitate kinetic forces much greater than those that can be generated by organisms of our dimensions. While significantly larger android beings could exert greater kinetic forces, the design of a bipedal primate of, say, twice our height would be severely constrained by kinetic and gravitational forces and be structurally problematic. 

Why? For one, mass (and weight) increases by the length cubed (L³) while the strength of bone and the power of muscles increases only by the length squared (L²). J. B. S. Haldane alluded to this with characteristic lucidity in his essay “On Being the Right Size”:

Consider a giant man sixty feet high — about the height of Giant Pope and Giant Pagan in the illustrated Pilgrim’s Progress of my childhood. These monsters were not only ten times as high as Christian, but ten times as wide and ten times as thick, so that their total weight was a thousand times his, or about eighty to ninety tons. Unfortunately, the cross-sections of their bones were only a hundred times those of Christian, so that every square inch of giant bone had to support ten times the weight borne by a square inch of human bone. As the human thigh-bone breaks under about ten times the human weight, Pope and Pagan would have broken their thighs every time they took a step. This was doubtless why they were sitting down in the picture I remember.

There is yet another kinetic constraint on being too big, arising again from the fact that kinetic energy is proportional to L⁴. Went explains:

The numerical values of kinetic energy actually give us a good clue as to the optimal size of man. A 2 m tall man, when tripping, will have a kinetic energy upon hitting the ground 20–100 times greater than a small child who learns to walk. This explains why it is safe for a child to learn to walk; whereas adults occasionally break a bone when tripping, children never do. If a man were twice as tall as he is now, his kinetic energy in falling would be so great… [16 times more than at normal size] that it would not be safe for him to walk upright…. The larger mammals can become taller, because they are more stable on their four legs. Yet, they break bones more easily when they fall.

As Steven Vogel puts it in Comparative Biomechanics, “Tripping is a potential danger to cows, horses, and the like… we run a similar risk even at a lower body mass; the upright posture of humans gives us an unusually great height relative to our mass.” He summarizes the larger point by recourse to the old saying, “The bigger they are, the harder they fall.”

Consequently tripping and falling would be a catastrophe for Pope or Pagan as their massive heads (1,000 times the volume of a human head) would hit the ground with such force that the skull would be fragmented and the brains disintegrate.

The Wheel Has Turned

With the evidence of our unique fitness for fire-making, which allowed humankind to take the first and fateful step along the unique path to an advanced technological civilization, the picture is complete. Nature is uniquely fit not just for our biological being, for our aerobic terrestrial existence, and for our size and body plan, but also for our unique capacity for fire-making and for following the singular path through metallurgy to an advanced technology and a profound understanding of nature. 

That claim can only be challenged by showing that, given the laws of nature and the structure of the cosmos, there is the possibility of fundamentally different types of biological life than ones based on carbon and water, the possibility of fundamentally different types of intelligent beings capable of making and controlling fire, and fundamentally different routes to an advanced technology and deep knowledge of the world, routes that do not pass through fire-making and metallurgy. However, no credible alternatives of this sort have ever been proposed. No single book or paper exists which provides a well-worked-out blueprint for a cell radically different from the canonical carbon-based cell, the basic building block of all life on Earth. No single paper or book exists which describes within the domain of carbon-based life an alternative biological design for an advanced organism comparable to modern humans possessed of a high metabolic rate and high intelligence. Nor has an alternative design ever been proposed in any detail for an advanced intelligent aerobic organism capable of making and controlling fire. Nor is there a single paper which describes a substantially different route to an advanced technology and ultimately scientific knowledge. One can imagine variations on the humanoid theme, of course, some more realistic than others. But to the degree that they are credible, they will be variations very close to the human form.

Even though many mysteries remain, we can now, in these first decades of the 21st century, at last answer with confidence Thomas Huxley’s question of questions as to “the place which mankind occupies in nature and of his relations to the universe of things.” As matters stand, the evidence increasingly points to a natural order uniquely fit for life on Earth and for beings of a biology close to that of humans, a view which does not prove but is entirely consistent with the traditional Judeo-Christian framework. Humankind’s exile from nature, which to many people’s minds commenced in the 16th century with the demise of the geocentric model of the universe, itself appears to be meeting its demise as evidence mounts that the logos, the underlying rationality of all things, is indeed “manifest in human flesh.” 

The wheel has turned. As I show in The Miracle of Man, scientific advances beginning with the flowering of chemistry in the 19th century and continuing at an ever-increasing pace through the 20th century and now into the 21st have vindicated the ancient covenant and revealed humanity to be as the medieval scholars believed, reflective in the depths of his natural being of all facets of the greater macrocosm of which he is an integral part. And in one of history’s supreme ironies, it is now the denial of humankind’s special place in nature, the foundational denial of the current secular culture and Zeitgeist, which grows increasingly outdated and devoid of empirical support.