Q. What do you mean by “superintelligence”?

A. Nick Bostrom defined superintelligence in 1998 as “an intellect that is much smarter than the best human brains in practically every field, including scientific creativity, general wisdom and social skills”. This isn’t incredibly specific, because “much smarter” depends entirely on what you mean by “much”. A stubborn skeptic might exclude any future being from the category simply by refusing to grant that entity X is “much” smarter than humans. The definition of “much” is necessarily subjective, but after a certain point, it seems likely that more than 90% of a survey population would agree on what “much smarter than the best human brains” means.

Allow me to create a more specific definition. I propose that superintelligence be defined as a being at least as smarter than Homo sapiens as we are smarter than Homo heidelbergensis. Why Homo heidelbergensis? According to the current consensus, H. heidelbergensis is the most recent known ancestor of modern day H. sapiens. Our species diverged from H. heidelbergensis about 400-200,000 years ago. This puts the species comparatively closer to us than more famous members of genus Homo including H. erectus (split 1.2 mya) and H. habilis (split at least 1.5 mya).

Of course, this definition is not perfect. The fossils that anthropologists call H. heidelbergensis are distributed over a 350,000-year period — between about 600,000 and 250,000 years ago, with considerable variation across that period. While this is a specific time window relative to most fossil species, it’s still a substantial period of time, and H. heidelbergensis has been accused of being a “wastebasket taxon”. The origin of the category is those problematic fossils with both “erectus-like” and “modern” features, formerly called Archaic Homo Sapiens. Traits of some specimens are listed here. One of the distinguishing features is a larger cranial capacity than earlier Homo species — approximately 1200 cc, relative to the modern human average of 1350 cc.

Still, because H. heidelbergensis is considered by most scientists to be a valid species, for which there is substantial fossil evidence, it provides a concrete reference point in the interspecies intelligence space. We can define “intelligence” using the wiktionary definition, “Capacity of mind, especially to understand principles, truths, facts or meanings, acquire knowledge, and apply it to practice”. H. heidelbergensis had it, as is demonstrated by the stone tools and evidence of organized hunting left behind, and H. sapiens obviously has it in even greater measure. Consider another species, H. novus, with an equal measure of greater intelligence relative to humanity. Intelligence may not be quantifiable on a linear scale, but that does not prevent this definition from being useful in a qualitative sense.

According to my source on Homo heidelbergensis, “The increase in brain size may have also come with an increase in brain complexity, although this is difficult to determine from endocasts, and may have to remain supposition only. However, the increase in absolute size, and the change to larger frontal and parietal lobes indicate that there may have been a reorganization of the functional anatomy of the hominid brain. The increase in size itself indicates changes in behavior that lead to the ability to more easily acquire nutritional resources. This is due to the high nutrition requirements of brain tissue, especially during development. There is increasingly more convincing evidence in the use and control of fire, and in the hunting of animals for food. This time period is important for many reasons, and may be the time period when more modern behavior began to develop.”

There were obviously major changes in the hominid brain around this time, but in the case of Homo heidelbergensis, it apparently wasn’t enough to launch the cognitive revolution ushered in by H. sapiens when it appeared on the scene about 200,000 years ago. This distinct failure should not go unnoticed. If the cognitive solution space were structured differently, Homo heidelbergensis might have had the capacity to develop agriculture and a global civilization, as H. sapiens eventually did. If so, we’d all be members of Homo heidelbergensis, and H. sapiens might never have evolved, the fast clip of hominid cognitive evolution being cut off by its own success. Phenotypic change happens fastest when there is strong selection pressure and beneficial alleles to evolve towards, but the triumph of H. sapiens over our environment has lifted the intense selection pressure experienced by our ancestors. The evolution of new human species via natural means now appears unlikely.

Because Homo heidelbergensis lived only a few hundred thousand years ago, it may be possible to recover enough DNA to revive the species and create living individuals. If so, then the cognitive performance of this species relative to modern humans could be directly compared. Until then, we will have to settle with what we know about the species from fossil and other archaeological evidence. Homo heidelbergensis produced Acheulean stone tools, also known as Mode 2, the second of four divisions of prehistoric stone-working industries. Mode 1 tools were Clactonian or Oldowan tools, which consisted of simple choppers and unretouched biface hand axes. Mode 2 tools consisted of retouched biface hand axes with an average useful cutting edge of 20 cm (8 in), relative to the less useful 5 cm (2 in) average of Mode 1 tools. Mode 2 tools are associated with H. erectus, Homo heidelbergensis, and other pre-human hominins. Mode 3 tools are Mousterian tools, which use the prepared-core technique. Mode 3 tools appeared just 200,000 years ago and are only associated with humans and Neanderthals. Mode 4 tools include the more spectacular lithic blades and are associated with human cultures from the Upper Paleolithic.

For the sake of simplicity, let us assume that Homo heidelbergensis never would have been able to develop Mode 3 tools, even if given millions of years to do so. Indeed, Mode 3 tools were invented practically immediately after the evolution of H. sapiens. A corollary of this is the claim that Homo heidelbergensis would never have been able to develop behavioral modernity, agriculture, or cities. If Homo heidelbergensis were alive today, it would almost certainly be considered too stupid to qualify as legally human, but it would probably occupy a unique intermediary role between humans and other living animals such as chimps. Whether Homo heidelbergensis had language is entirely unknown, but it might have. At the very least, its system of grunting and other non-verbal communication would likely have been substantially more complex than that of chimps or gorillas.

My definition of superintelligence is just an interesting and slightly more specific way of looking at the concept than the standard definition. It makes no specific claims about the form of a possible H. novus, just that it would be broadly smarter than us in the way that we’re smarter than Homo heidelbergensis. I advance the concept as a starting point for debate. Under this definition, there are those that might consider superintelligence impossible, and those who might consider it possible. Sometimes the word “superintelligence” is associated with entities like Jupiter Brains, so this new definition provides a service by offering a less radical and more easily defensible position. Personally, it seems difficult to deny the in-principle possibility of superintelligence under this definition, but many would likely disagree with me.