Expansion of the human frontal cortex and endocranial volume, to which we likely owe our capacity for abstract thought, predominately occurred between 50 000 and 500,000 years ago in our prehistoric African ancestors, well before written language and before we had the modern voice-box to produce sophisticated verbal language, but after the first tools. Thus, the selective pressures that gave us our mental characteristics operated among nonverbal hunter-gatherers living in dispersed bands or villages, nothing like our present-day high-density, supportive societies.
Many kinds of modern refined intellectual activity (by which our children are judged) may not necessarily require more innovation, synthesis, or creativity than more ancient forms: inventing the bow-and-arrow, which seems to have occurred only once about 40,000 years ago, was probably as complex an intellectual task as inventing language. Selection could easily have operated on common (but computationally complex) tasks such as building a shelter, and then computationally simple tasks, such as playing chess, became possible as a collateral effect.
AI promised household robots that would wash dishes, mow the lawn, and bring us freshly cooked croissants and coffee in the morning. Needless to say we do not have these robots now and none of the readers of this piece will probably ever see them, despite the immense financial impetus to build them.
A hunter–gatherer who did not correctly conceive a solution to providing food or shelter probably died, along with his/her progeny, whereas a modern Wall Street executive that made a similar conceptual mistake would receive a substantial bonus and be a more attractive mate. Clearly, extreme selection is a thing of the past.
Our fragile intellect. Part I
by Gerald R. Crabtree
Trends in Genetics
Volume 29, Issue 1, p1–3, January 2013
**
Our fragile intellect. Part II
by Gerald R. Crabtree
Trends in Genetics
Volume 29, Issue 1, p3–5, January 2013
**
New developments in genetics, anthropology, and neurobiology predict that a very large number of genes underlie our intellectual and emotional abilities, making these abilities genetically surprisingly fragile.
Crabtree Laboratory: Developmental Genetics, Chemical Biology, Signaling and Chromatin Regulation
Stanford University
http://crablab.stanford.edu/
Gerald Crabtree
Wikipedia
https://en.wikipedia.org/wiki/Gerald_Crabtree
“Our Fragile Intellect”
“Our Fragile Intellect” is a 2012 article by Crabtree, published in the journal Trends in Genetics. Crabtree’s speculative and controversial thesis argues that human intelligence peaked sometime between 2,000 and 6,000 years ago and has been in steady decline since the advent of agriculture and increasing urbanization. Modern humans, according to Crabtree, have been losing their intellectual and emotional abilities due to accumulating gene mutations that are not being selected against as they once were in our hunter-gatherer past. This theory is sometimes referred to as the Idiocracy hypothesis.
Thesis
Crabtree argues that advancements in modern science allow new predictions to be made about both the past and the future of humanity and we can predict “that our intellectual and emotional abilities are genetically surprisingly fragile”. Recent studies of genes correlated with human intelligence on the X chromosome indicate typical intellectual and emotional activity depends on 10% of genes. Intelligence-dependent (ID) genes appear to be widely distributed throughout the entire genome, leading to a figure of 2,000 and 5,000 genes responsible for our cognitive abilities. Deleterious mutations in these genes can impact normal intellectual and emotional functioning in humans. It is thought that in just the last 120 generations (3000 years), humans have received two or more harmful mutations to these genes, or one every 20-50 generations.
Several counterarguments are presented. The Flynn effect, for example, shows an apparent increase in IQ around the world since 1930. Crabtree attributes the rise in IQ to advancements in environmental and public health measures as well as improved education and other factors. The Flynn effect also shows, argues Crabtree, not an increase in intelligence, but more intelligent test taking.
Reception
Kevin Mitchell, associate professor at the Smurfit Institute of Genetics at Trinity College Dublin agreed that genetic mutations could harm the development of the brain in humans and diminish intelligence; new mutations would become apparent in new generations. However, Mitchell criticizes Crabtree for failing to acknowledge the role of natural selection. According to Mitchell, natural selection “definitely has the ability to weed out new mutations that significantly impair intellectual ability”. Mitchell describes Crabtree’s argument as a conceptual fallacy and says Crabtree is “thinking about things in a wrong way”.
Biologist Steve Jones, Emeritus Professor of Genetics at University College London questioned the journal’s decision to publish the paper, calling the study “a classic case of Arts Faculty science. Never mind the hypothesis, give me the data, and there aren’t any”. Crabtree acknowledges that the data isn’t there because a slow genetic deterioration in intelligence can’t be detected by comparing it to people today. Instead, Crabtree argues that he is synthesizing already existing data and making a purely mathematical argument that estimates the probability of the number of new mutations that could result in cognitive deficits in future generations.
Anthropologist Robin Dunbar at Oxford University argues against Crabtree’s position that brain size was driven by tool use. Instead, Dunbar argues that the social environment drives intelligence. “In reality what has driven human and primate brain evolution is the complexity of our social world”, says Dunbar. “That complex world is not going to go away. Doing things like deciding who to have as a mate or how best to rear your children will be with us forever.”
Cultural trope
Writer Andrew Brown notes that Crabtree’s paper represents a familiar, reoccurring notion in both fiction and evolutionary biology. “The idea that civilised man is a degenerate and self-domesticated variation on the wild type is partly a cultural trope, a result of the anxieties of industrialised life,” writes Brown. The idea, Brown observes, was popular in the early 20th century fiction of E. M. Forster (“The Machine Stops”) and Jack London (The Scarlet Plague). It could also be found in the work of biologists such as Ronald Fisher, who espoused similar concepts in The Genetical Theory of Natural Selection (1930). The most important parts of Fisher’s book, Brown writes, expounds on the theme that “civilisation is dreadfully threatened by the way the lower classes outbreed the aristocracy.” Brown finds related sentiments expressed in the work of W. D. Hamilton, who believed that the “life-saving efforts of modern medicine” threatened the human genome.
Homo (Sans) Sapiens: Is Dumb and Dumber Our Evolutionary Destiny?
by Gary Stix
http://blogs.scientificamerican.com/talking-back/homo-sans-sapiens-is-dumb-and-dumber-our-evolutionary-destiny/
James R. Flynn’s observation that IQ scores experienced dramatic gains from generation to generation throughout the 20th century has been cited so often, even in popular media, that it is becoming a cocktail party talking point. Next stop a New Yorker cartoon. (An article about Flynn and the Flynn effect has already been published in The New Yorker.)
A recent report in Trends in Genetics (part 1 and part 2) takes a bleaker view of our cognitive future—one that foresees the trend line proceeding inexorably downward. Gerald Crabtree, a biologist at Stanford University, has put forward a provocative hypothesis that our cushy modern existence—absent the ceaseless pressures of natural selection experienced during the Paleolithic—makes us susceptible to the slow creep of random genetic mutations in the the 2000 to 5000 genes needed to ensure that our intellectual and emotional makeup remains intact. The implications of this argument are that we as a species of the genus Homo are over many generations slowly losing our sapiens.
The press justifiably had a field day with this one:
Why did Petraeus do it? Maybe humans are evolving to be dumber.
We’re getting, like, dumber
Homo уже не тот sapiens
The really clever part of Crabtree’s argument rests on the contention that a Stone Age Fred Flintstone may have been more of a dynamo in some ways than a 20th century Albert Einstein—our pre-historic forebears performed the evolutionary heavy lifting that led to the swollen heads that we still avail ourselves of, at least until the inevitable decline predicted by Crabtree sets in.
In line with Crabtree’s take, the transition to survival through wiles—in place of speed and physical strength—required adaptations that appeared to rival or outpace the most lofty contemporary intellectual achievements like writing a symphony or cogitating on higher math. One small error in gauging the aerodynamics and gyroscopic stabilization of a spear and one of our would-be ancestors became a canape for a saber-tooth tiger.
Flintstone vs. Einstein smarts are contrasted most starkly by considering the case of artificial intelligence. AI has achieved major strides in emulating certain aspects of intellect: playing chess or Jeopardy and finding patterns in large collections of data, a field dubbed “deep learning.” But the remaining and still immense challenges AI confronts lie elsewhere, as Crabtree points out:
The things at which AI excels—playing chess, Jeopardy or keeping an airplane on course—are, in fact, a cognitive piece of cake compared to washing dishes and putting them away in the right place. I remember roboticist Rodney Brooks demonstrating this during a talk at MIT in which he simply put his hand in his pocket and pulled out some change, an extraordinarily tough task for the current generation of R2-D2s.
Without the rigors of strong selection in our extended urban conglomerates—no more necessity of getting it right the first time on that spear throw—the slow but relentless decline of those 2,000 to 5,000 cognition-related genes has already begun—as this argument goes. Crabtree begins the first part of his essay by asserting that the average citizen from Athens circa 1,000 B.C.—or anyone from Africa, India, Asia or the Americas millenia back—would be among the “brightest and most intellectually alive of our colleagues and companions, with a good memory, a broad range of ideas, and a clear-sighted view of important issues”—personal qualities supplemented by an astonishing emotional aplomb. This hyper-fit type would have prevailed even before the rise of civilization:
Maybe this explains our fascination with post-apocalyptic Mad Max-style fantasies? But where’s the proof for Crabtree’s musings and what about contradictory evidence? Crabtree proposes a test of his hypothesis and he also dismisses the Flynn effect that suggests that we have been getting progressively smarter generation after generation. Better IQ scores, Crabtree posits, are not a result of natural selection, but rather may have resulted from getting rid of lead and other heavy metals from gasoline and paint, from elimination of hypothyroidism by putting iodine in salt and from learning how to take tests better. Notwithstanding the Flynn effect, our slow genetic decline continues apace.
And what does the author of the Flynn effect think about the Crabtree effect?
Meanwhile, noted British anthropologist and evolutionary psychologist Robin Dunbar questions the premises of any postulated slow slide toward imbecility:
The question, as often happens in evolutionary biology, is how to distinguish assertions like Crabtree’s from a Rudyard Kipling “just so” story. Crabtree has thought of a test that would sequence whole genomes of carefully selected individuals—ones whose genes could be traced back through an involved analysis to ancestors who lived at different times during the past 5,000 years when the transition from hunter-gatherer lifestyle to agriculture was taking place. The test would look for an increase in mutations for those individuals with genes linked to ancestors who lived more recently along the 5000-year continuum, a confirmation of the gradual decline in intellectual ability.
Finding these people might require more than posting notices on Twitter and Facebook and Crabtree’s proposal is probably not going to get pegged high on the NIH’s funding priorities for the 2014 federal fiscal year. But the Stanford professor still does not despair. He ends this entropic projection of our evolutionary future on an optimistic and self-deprecatory note. Science, he says, may yet find a way to counteract this trend. “One does not need to imagine a day when we could no longer comprehend the problem, or counteract the slow decay in the genes underlying our intellectual fitness, or have visions of the world population docilely watching reruns on televisions they can no longer build.”
We may still have a few hundred years before we lose the modifier denoting “intelligent” in Homo sapiens and science may yet find a way to save us “by socially and morally acceptable means. In the meantime [Crabtree volunteers], I’m going to have another beer and watch my favorite rerun of Miami CSI (if I can figure out how to work the remote control).”
Study: Human Intelligence Is No Longer Needed To Survive
by Julian Sonny
Elite Daily
http://elitedaily.com/news/world/study-human-intelligence-diminishing-longer-survive/
Human intelligence, which was once thought would grow exponentially until every last being on earth was a genius, is in a general decline, as it is not necessary for human functionality in the 21st century.
Stupid Humans
by Adam Goldfein
http://adamgoldfein.com/stupid-humans/
In Our Fragile Intellect, published in Trends in Genetics, Crabtree suggests that humans reached their intellectual peak about 2,000 to 6,000 years ago. “The expansion of the human frontal cortex and endocranial volume, to which we likely owe our capacity for abstract thought, predominately occurred between 50,000 and 500,000 years ago…” Crabtree says. Selective pressures of survival required ancient hunter-gatherers to develop the intellectual capacity capable of an intuitive understanding of the aerodynamics of a spear and making snap life-or-death judgments when hunting large, dangerous animals. Inventing the bow and arrow may have required more intelligence and innovation than landing on the moon.
These pressures, which Crabtree suggests formed and maintained our intellectual capacity, are absent in structured society. He believes that living in high density society after the invention of agriculture began the decline of human intelligence, as each individual no longer had to rely on their intellect as much to survive and procreate. Supportive societies allow for lapses in judgment and failures of comprehension. Community life in general reduces “the selective pressures placed on every individual, every day of their life,” Crabtree says. “A hunter–gatherer who did not correctly conceive a solution to providing food or shelter probably died, along with his/her progeny, whereas a modern Wall Street executive that made a similar conceptual mistake would receive a substantial bonus and be a more attractive mate. Clearly, extreme selection is a thing of the past.”
人類はバカになり続けているのか 知性のピークは2000～6000年前説
J-CAST ニュース
http://www.j-cast.com/2012/11/23154999.html
人間の知性は2000～6000年前がピークだった―。こんな論文を、米スタンフォード大学の教授が発表した。人類が狩りをしなくなったため、知的、感情的能力が、徐々に衰えているのだという。
近代以降、人間の知性は進化しているとばかり考えられてきた。そのため、ネットでは「信じられない」という声が相次ぎ、「ゲームで狩りをすればいいのか」といった発言も飛び出した。
知能の低くなった人間が淘汰されることが少なくなった？
スタンフォード大学の遺伝学者ジェラルド・クラブトリー教授が、
「人間の知性は2000～6000年前にピークを迎えており、その後人類の知的、感情的な能力は徐々に衰えている」
との研究結果を発表した。論文は、米科学誌セルの関連誌「Trends in genetics」(2012年11月13日号）に掲載された。
それによると、人類は狩猟採集社会で生きてきた数千年前に、進化の99％が止まってしまったそうだ。これは脳の大きさの変化から明らかだという。そしてこれ以降、人類が都市に定住するようになってから今にいたるまで、知的・感情的能力がともに落ち続けていると主張した。
教授は理由をこう書いている。
人類の知性の形成には2000から5000という多数の遺伝子が関係し、それらは突然変異により、働きが低下する危険にさらされている。狩猟社会では、知的・感情的な能力のある人間しか生き残れなかったが、歴史の中で農業や都市が発明され、命が脅かされるリスクが減った。これにより、遺伝子の突然変異で知能の低くなった人間が自然淘汰されることが少なくなった。その結果、人類の進化としての脳の拡大が止まり、知能が低下し続けているのだという。
「一瞬、虚構新聞の間違いではないかと」
人間の知能は進化してきたと素朴に信じられてきただけに、ネットでは、
「失礼な」
「マジすか…こんなに大量の情報を扱っているのにか？」
「一瞬、虚構新聞の間違いではないかと疑ってしまった」
といった「信じられない」とする反応が相次いだ。
また、狩猟をしなくなったからという理由に「モンハンやれってことか」という人も現れた。モンハンとは人気ゲーム「モンスターハンター」の略で、名前の通りモンスター「狩り」をして遊ぶ。
ただ、論文の内容に疑問を示す人もいる。米Independent紙では、ロンドン大学の遺伝子学者スティーブ・ジョーンズ教授が「ただのアイデア。証明するデータがないし、どうやって調査すればいいのかも分からない」などと一蹴した。
日経サイエンス（12月号）のコラム「知能は延び続けているか」では、IQテストの平均スコアは1年に0．3ポイント、10年で3ポイントのわりで着実に伸びているという「フリン効果」を紹介した。伸びているのは主に抽象推論を試すテストや、幾何学図形の類似性を問うなど抽象思考を試すテストで、現代においては社会生活を営む上で抽象的な思考が必要とされているから考えられているという。そして、「将来は、あなたも私もひどく前近代的で想像力の欠けた人物に見えるような世界になるのだろう」と結んでいた。
「どっちが正しいのか」に結論を出すのは難しそうだ。