Technology is adaptive, cumulative, and generally progressive. At its simplest, it is older than reason; at its most advanced, it is the product of cooperative undertakings by large numbers of highly intelligent organisms.
Though the word is now used loosely, technology can most conveniently be defined as the systematic study of tools: a technological species is any species of animal that uses tools. Tools must be clearly distinguished from artefacts. Artefacts are common in the animal kingdom-birdnests, beehives, and beaver lodges are among the finest examples-and they are made by some creatures quite low in the evolutionary scale (such as the caddie fly larva, that makes cases and nets). Tools are distinct from artefacts because they can be used to make other objects or to facilitate activities such as resource extraction. They are not by themselves of immediate and direct use.
If we are to assess the probability of technology developing on other planets, it would appear most useful to discuss the origins of terrestrial technology, its simplest forms, and the factors that made possible its extraordinary development.
It is now well known that the use and modification of tools is not confined to man. Examples include the Galapagos finch Cactospiza, which uses a cactus (prickly pear) spike to poke out insects embedded in the branches or trunks of trees. Where there are no cacti, Cactospiza breaks off a short stiff twig from a tree. A second example is the British Greater Spotted Woodpecker (Dendrocopos major), which pecks out a V-shaped cleft in a tree trunk and uses it to anchor pine cones, oak-apples, etc., while it extracts seeds or insects. These are two examples of tool modification found among birds, but there may be many others.
 Tool use (though not modification) has been identified among insects. Most striking is the use by the solitary burrowing wasp Ammophila of a small pebble to firm up the sealed entrance to its burrow. When the wasp has filled the burrow with eggs and a food supply of caterpillars, it seals the burrow and covers it with sand grains hammered firmly into place. In the end, all trace of the nest is obliterated.
These examples from the insects and birds illustrate the two stages of what I shall call prototechnology (table 1).
a. Tool use
b. Tool modification
a. Tool manufacture
b. Stone technology (secondary tools)
a. Fire control and fire making
b. Metal industries (smelting, forging, casting)
a. Containers, cord, etc.
b. Energy control
Category 1a Includes the use of found objects as tools. To our introductory examples we can add the famous example of the sea otter (Enhydra), which floats on its back with a stone on its chest, opening shellfish such as abalone by smashing their shells with the stone. These examples of tool use imply that certain qualities belong to the species that use them: the existence of manipulative organs (a beak and forelimbs on our examples), a good visual sense, and a behavioral flexibility that permits discovery and invention-although at a very simple level. The activity is in most cases a solution to a problem of obtaining environmental resources, but in the case of the wasp it presumably improves reproductive success. In the instances of the finch, the woodpecker, and the otter, important new food resources are available as a result of tool use.
It is important to stress this point: the motive must be present as well as the potential. Tools allow these animals to tap food resources not otherwise available to them, and tools give them great advantage in that they then have a monopoly or near monopoly of that particular resource. This freedom  from competition is a very desirable and rare biological state. The phenomenon of tool use is not confined to mammals and therefore does not require a very highly evolved central nervous system.
The second stage of prototechnology (category 1 b) involves the natural Object specially modified for tool use. The classic example here is the chimpanzee, which modifies grass stems or twigs for termite fishing. The twigs are collected, any leaves are removed, and the length is adjusted to a standard. Less well known is the chimpanzee's preparation of leaves by chewing to make them act like a sponge to absorb water in order to drink from an awkward place such as a hole in a tree trunk. This category clearly represents a distinct advance in the history of technology and implies not only discovery and imagination but foresight. Thus the preparation of a twig by breaking one of an appropriate length by Cactospiza is a remarkable fact. One might have expected that a highly evolved central nervous system was essential for this development. It is certainly very rare among animals. Among chimpanzees it is transmitted by learning: this is highly significant since it allows rapid modification of technique and thus rapid development of technique. Whether it has become a programmed behavior among finches, as distinct from a learned one, which is how it must have begun, is not known
Stage 1a does not easily lead to 1 b and indeed does not logically imply such development. Stage 1b, however, has immense potential, and while in the chimpanzee it has not led to further advances, there seems every reason to believe that it will give its practitioner the potential to develop true tech
The earliest evidence we have of humans making tools is, of course, lithic. This, however, should not lead us to suppose that stone tools were the first human tools. Modern tribal peoples only have a small percentage of material culture that will be preserved in an archaeological site. The vast majority of the technology is biodegradable: besides stone, simple tools are made of bone, antler, horn, teeth, wood, and leather.
The difference between categories 1b and 2a may seem very slight at first, but in practice there is a world of difference between modifying a twig and removing its leaves (for the twig existed in the first place and could be clearly seen) and making a pebble into a knife-like object for chopping or cutting. This surely requires far greater imagination. However, stone choppers and stone flakes do occur naturally and can be produced by dropping one stone on another by chance. Sharp stone flakes were in our environment a billion years before hominids found a use for them. When they did - where the motive was present and the brain sufficiently developed-then the step from the use of existing objects to tool manufacture might have been rapid. Whatever other biodegradable technology such as digging sticks, rakes, and levers they may have had, the use of stone cutters and choppers would have opened up a vast new food resource-not free of competition  but otherwise unavailable to a hominid lacking a carnivorous dentition or powerful canine teeth. The food resource took the form of large mammals.
The manufacture of stone tools depended essentially on motive and manipulative skill, neither of which at first need have been highly developed. But it led to a most important development: because stones were so hard, they could be used to cut other softer (yet quite hard) materials such as wood and bone which, in turn, could be used as tools.
Thus simple stone tools such as flakes and choppers could become , almost immediately, secondary tools (stage 2b). In this way, human technology began its extraordinary development.
Let us stop here for the moment and review the essential factor involved in this development:
1. A lead-in from the prototechnology of stone; that is the use of naturally occurring flakes and choppers.
2. Observation of natural examples of stone tool-making by percussion, that is; the effects of falling or dropped stones.
3. The existence of a motive related to cutting tool use, namely, the addition of large mammals as a food resource.
4. The availability of raw materials in certain areas.
5 The hardness of raw materials, allowing development of tool-making, as well as good cutting edges.
6. The generation by the central nervous system of a good visual sense, imagination and foresight, behavioral flexibility, learning potential, and motor skill.
From approximately 2 million years ago, we can see the development of lithic technology in the archaeological record. As this development accellerated- and it accelerated incredibly slowly from our viewpoint-we find evidence of the unfolding of human skill, imagination, and ingenuity. The stone technology was no doubt accompanied by a wonderful proliferation of biodegradable tools. With few exceptions these have not been preserved from the earliest days, and for most of human prehistory technological data are confined to stone tools. However, we should record the following: first prepared bone point, Olduvai (Tanzania), about 1.75 million years ago, first prepared wood spear point, Clacton (England), about 300,000 years ago; first bone tool kit, Choukoutien (China), 400,000 to 500,000 years ago. Such evidence is meager but suggestive of the extent of such tool kits.
Although stone tools are not known much before 2 million years ago, tool manufacture must be very much older, and tool modification and tool use older still. We have no good evidence of this earlier phase of human prototechnology, although Louis Leakey claimed that he had evidence of bone bashing with a rounded and battered cobble, on an ancient land surface  at the site of Fort Ternan, dated about 14 million years ago. The progression 1 a -> 1 b -> 2a -> 2b seems an eminently reasonable assumption.
The next landmark is probably the most important one since it introduced the possibility of sophisticated metal technology. I refer to the capture, control, and eventual making of fire (stage 3a). Pyrotechnology probably had a very slow beginning: the generation of wild fire through lightning, the Sun's rays, oil seeps, etc., is rare enough, but its capture must have been even less common. Following capture, the fire needed to be controlled and fed. Why should the task ever have been undertaken? Two motives seem compelling: curiosity and the need for warmth. Curiosity might well have led men to capture fire and play with it, but only the need for warmth could lead man to capture and feed fires for weeks, months, and even years.
The earliest evidence of fire in the archaeological record is important. The two sites with the clearest hearths are those of Vertesszollos in Hungary and Choukoutien near Peking. In both areas, humans were hunting and gathering in a temperate environment with cold winters. The Hungarian site is open, the Chinese site, a cave used for habitation. The dates are probably both in the period 400,000 to 500,000 years ago. At Choukoutien there is also evidence of burnt bone, which implies roast meat. At Vertesszollos, the hearths are not very large: the site is a butchery site. At Choukoutien, the cave deposits are immensely deep and the hearths contain many meters of ash superimposed: evidently the fires were permanently maintained throughout the year. (The validity of earlier evidence of fire from L'Escale Cave in the south of France about 700,000 years ago has been questioned.)
Fire is not recorded from Africa until very much later: about 60,000 years ago, at Kalambo Falls. While there is no shortage of earlier archaeological living sites in Africa, fire is always absent. There was evidently no reason to capture and control it. It seems fairly certain that the development of pyrotechnology was a correlate of a temperate climate. It led to new techniques of tool-making and hunting, and it also gave protection from predators (especially the cave bear that competed for living space); it gave light and a means of cooking. But almost certainly the most important factor was warmth.
In the manufacture of tools, fire has many uses, from the breaking of large stones by heating and sudden cooling to the hardening of spear points (stage 3b). By far the most important technological development was the smelting of metal ores (copper and tin), first recorded in eastern Europe about 4,500 years ago, some 500,000 years after the first indication of fire use Here again a motive must have existed to produce copper in large quantities and such need could hardly have developed until naturally occurring metallic gold, silver, and copper had been in use for some time. Copper smelting at its simplest merely implies putting some malachite in a hot fire  but recognition of the value of the product was needed to bring about regular production. This is a general rule: a species will not make a tool unless its value has been clearly established. The idea of tool research and development is very recent in human history. Metals were not smelted in Africa south of the Sahara, Australia, or America until the technique was introduced from Europe. Europeans were most probably the inventors of smelting and alloying, and they have since led the rest of the world in metal technology.
The geographer Philip Wagner defined a class of objects he termed facilities as objects that restrict or prevent motion or energy exchanges (stage 4). Examples include containers, dams, boats, fences, cords (stage 4a) and anything that insulates and retains heat, such as clothing, shelters, or tents (stage 4b). This is an extremely important class of artefact distinct from simple tools; but since many tools operate by altering energy flow in some way, the distinction is not absolute.
What is important is that the simplest facilities so defined were unquestionably of the greatest importance in human evolution, particularly in temperate zones. They become an essential component in any evolving technology, and the principles involved in this class of artefact become quite important in human technology generally.
A further subcategory of tools is machines, which are complex tools with moving parts. Either the spear thrower (about 14,000 years ago) or the bow and arrow (about 10,000 years ago or more) might qualify as the earliest examples.
Finally, toys may be defined as tools used for play, that is, for experimental purposes. Play, which is seen in many mammals, especially carnivores and primates, has had an extremely important part in human evolution. Play depends on leisure, or freedom from a constant concern with the search for resources. In play, young primates test their own physique, the social responses of their peers and elders, and their environment. When tools are used, the young will play with them and even attempt to make them. Play tools or toys are made for experimental and exploratory activities. Play is the activity in which innovative behaviors are established and new artefacts are incorporated into a culture.
In this brief review of terrestrial technology, we have traced a few simple but important steps that have led to the manufacture of radiotelescopes. In human evolution, each of the stages in groups 1 and 2 has followed the last in succession; but as we have seen, the development of this series is by no means inevitable. In insects and birds it is clearly blocked by  inadequate manipulative organs and insufficient intelligence. The development of facilities and fire was critical in the establishment of a metal technology. Adequate resources derived from agriculture were essential for the development of advanced technology. At all stages, the ratio of cost to reward had to be small and the technological development had to follow an appropriate cultural preadaptation. Play would unquestionably have been important in technological innovation. The history of toys has yet to be written, but it may be a key to an understanding of the progressive development of human technology
Having reviewed the nature of the development of simple terrestrial technology, we can return to examine its place in terrestrial prehistory. What factors made this development possible? The evolution of social groups as distinct from aggregations of individuals is by no means uncommon in terrestrial evolution. Primate-like social groups are evidently not essential preconditions for the evolution of tool use, and learned behavior patterns can be passed from parent to offspring in their absence. Such social groups do, however, facilitate certain aspects of technological development.
Social groups can be expected to occur whenever some or all of the following conditions are fulfilled:
- 1. Multiple channels exist for communication between individuals.
- 2. Food is either widespread and common or clumped.
- 3. Social cooperation is at a premium for some reason, such as protection from large predators.
- 4. The rapid spread of learned behavior is at a premium.
For technological progress, social groups have the following advantages:
- 1. More exploratory behavior and play.
- 2. Better learning conditions, with rapid spread of learned behavior patterns through a population.
- 3. Potential to exploit large "locked" food resources.
Primate-like social groups are clearly essential for the later and more advanced phases of technological development in which the cooperation of a number of individuals is essential to make and use tools. The important factors are the following:
- 1. Social groups should be well integrated.
- 2. The reward for tool development must be available in terms of valued resources.
- 3. The material resources needed to make the tool must be available (suitable stone, wood, etc.).
-  4. A social situation must exist which encourages invention and skill.
- 5. Individuals must have a good visual sense and manipulative skill.
It seems that the hominid adaptation of tool-making bipeds was a product of social primates with the following essential characteristics:
- 1. An advanced central nervous system, on both sensory and motor sides.
- 2. Some prototechnology.
- 3. A strongly motivated exploratory drive.
- 4. A rich and complex environment, with an extensive forest/savanna ecotone.
- 5. A potential for habitat and niche expansion, given the key (cutting tools) to a huge resource of savanna mammal meat.
The use of stone tools, recorded since 2 million years ago and associated with the genus Homo, at first evolved slowly, while humans were confined to tropical and subtropical regions. With the evolution of language and the development of the control of fire, humans entered temperate and eventually arctic regions, and these remarkable adaptations ushered in the appearance of Homo sapiens about 300,000 years ago. The development of technology from that time has allowed a vast expansion in the range and biomass of the species and the generation of an immense surplus of wealth (resources) in some regions. This surplus, based on agriculture and labor, has made possible the construction of radiotelescopes which themselves do not increase or facilitate resource extraction: they must therefore be defined as research tools or toys.
In an extraterrestrial context, we may predict that prototechnology is by no means uncommon where animals have evolved, but that full metal technology is likely to depend on the existence of a suitable social species. Should organisms with radiotelescopes exist, it seems reasonable to predict that they would carry most of the following characteristics:
- 1. Animal-like mobility.
- 2. Bilateral symmetry.
- 3. Heterotrophic nutrition.
- 4. Nervous systems.
- 5. Organs of manipulation.
- 6. Social groups.
- 7. Ability to learn and communicate efficiently.
- 8. Play and exploration.
- 9 Evolved visual sense.
- 10. Large and structured central nervous system.
- 11. Flexible behavioral response capability (intelligence).
- 12. Adaptations to rich, varied, complex environments.
- 13. An environment with seasonal variations in temperature.
 Moreover, they would have suitable raw materials present: metal ores, energy sources, and surplus food resources.
Technology is adaptive, cumulative, and generally progressive. At its simplest, it is older than reason. At its most advanced, it is the product of cooperative undertakings by large numbers of highly intelligent organisms.