英検1級に出そうな単語-When Hobbits Were Real
映画"ホビット"を知っていますか？
"ロード・オブ・ザ・リング"の前日譚のお話です。
私は小説の方で"ホビットの冒険"を読みました。
"ホビット"のように小さな人類の"ホモ・フローレシエンシス"のお話です。
英検に出てくる人類学の用語はかなり入っていると思います。
なれていないと難しい単語に感じるかもしれませんが、
よく目にする単語で、どれも覚えておきたいですね。
"anthropologist;人類学者"
"fossil;化石"
"hominin;ヒト族"→"hominidae;ヒト科"
"basal;基礎的な、根本的な"
"baffling;不可解な、困惑させる"→"baffle;困惑させる、失敗させる"
"collarbone;鎖骨"
"Homo sapiens;ホモ・サピエンス"
"homo erectus;ホモ・エレクトス、原人"
"specimen;標本"
"archaic;古い、古風な、すたれた"
"ape;類人猿、猿"
"australopithecine;アウストラロピテクス、猿人"
"bipedal;二足歩行の"
"stature;身長、成長、才能"
"proportioned;釣り合いの取れた"→"propotion;割合、調和、バランス"
"lineage;系統、家柄、血統"
"pelvis;骨盤"
"limestone;石灰岩"
"mammal;哺乳類"
"predator;捕食者"→"prey;被食者、獲物","raptor;猛禽類"
"strand;行き詰まらせる、座礁する"
"pygmy;ピグミー族、小人"
"stegodon;ステゴドン"
"formidable;恐ろしい、手に負えない"
"scavenge;漁る、清掃する"
"flake;剝片"
"pathological;異常な、病的な"
"indigenous people;先住民"→"indigenous;土着の、固有の"
"limb;四肢、手足"
"hypothesis;仮説"
"syndrome;シンドローム、病的現象"
"hormone;ホルモン"
"microcephaly;小頭症"
"circumference;円周、周辺"
"anatomy;解剖学"
"The Shire;ホビット庄"→ホビットたちが住んでいる村
"shire;イギリスの州"→"Yorkshire;ヨークシャー", " Hampshire;ハンプシャー"など
"shire"がつかない州も "Devon;デヴォン", "Kent;ケント"など
"parsimony;最大節約法"→生物の系統を解析する方法の一つ
"diverge;分岐する"
"statistics;統計学"
"consensus;一致、総意"
"artifact;遺物、工芸品、芸術品"
"deposit;堆積物、鉱脈、預金、保証金"
"eruption;噴火、噴出"
"extinct;絶滅した、消えた"
"remote;辺鄙な、人里離れた、遠い"
"excavation;発掘"
"ongoing;進行中"
"genetic;遺伝学の、遺伝の"
"unravel;解明する"
"molecular;分子の"
"collagen;コラーゲン"
全文-数字は動画の時間です
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In October 2004, our understanding of the human family tree was turned upside down.
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That’s when anthropologists reported that they’d discovered the bones of a tiny, unknown
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hominin, on the Indonesian island of Flores.
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This little creature stood only about a meter tall and had a brain about the size of a chimpanzee’s.
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But that wasn’t what was so shocking.
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We already knew about small-bodied, small-brained hominins in the human fossil record, like
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the australopithecines.
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What was really striking about this skeleton is that, at first at least, it appeared not
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to have been very old, and yet it had features of much older, more basal hominins.
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The original description of the bones dated them to between about 35,000 and 14,000 years
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ago, which means that they would have lived at the same time as us.
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But the last time a hominin with a brain that small was around, was millions of years ago
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- not thousands - well before modern Homo sapiens was on the scene.
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And the rest of its skeleton was equally baffling.
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Its shoulder joint wasn’t like that of any modern human.
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It had short collarbones, which meant that the shoulders were rotated forward in a way
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that hadn’t been seen since early specimens of Homo erectus, from around 1.6 million years
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ago.
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The three bones of its wrist that were found were also strangely archaic-looking.
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They were shaped like the bones of African apes and australopithecines - not like ours.
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And its feet were really long compared to the length of its legs.
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We’re talking ape-like, not human-like, proportions.
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And yet, it had short big toes and was probably an effective bipedal walker.
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Its discoverers named this puzzling hominin Homo floresiensis, but it’s often called
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“the hobbit” for its short stature and oddly proportioned feet.
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And it’s been at the center of a major controversy in the field ever since.
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It’s been fifteen years now since its discovery was first announced, and we’re still exploring
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what this little hobbit can tell us about the shape of the human family tree, and what
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it means for our own evolutionary history.
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And the questions that this little creature raises are big:
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Was it its own species?
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Or was it really just one of us?
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Or, could it even have descended from a whole lineage of hominins that we don’t even know
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about?
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The partial skeleton that started the whole controversy is called LB1.
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And it belonged to an adult female Homo floresiensis, based on the shape of her pelvis and the fact
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that her wisdom teeth had come in.
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But she’s not the only hobbit that anthropologists have found.
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Since her discovery, the remains of as many as 11 other members of her species have been
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recovered, although LB1 is still the only one with a skull.
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And all of these hobbits come from a single site: a limestone cave called Liang Bua, located
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in the western part of the island of Flores.
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So, when LB1 was discovered in 2003, one of the first things scientists had to figure
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out was how to explain her tiny size and strange mix of features.
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What branch of our family tree could’ve produced such an odd hominin - a hominin,
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by the way, being a primate that’s more closely related to us than to chimps?
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The team suggested that her species had evolved from a population of Homo erectus that became
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isolated on the island of Flores.
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And then, thanks to evolutionary pressures, their bodies got smaller over time.
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Now, there are fossils of Homo erectus from other Indonesian islands, and they cover a
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wide range of time -- from 1.6 million to just 143,000 years ago.
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So we know that Homo erectus made it to that part of the world.
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And we know that mammals on islands can change dramatically in body size over time, thanks
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to a phenomenon known as Foster’s rule, which we’ve talked about before.
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This rule says that big mammals on islands often get smaller, and small mammals tend
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to get bigger, as they adapt to limited resources and fewer predators.
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So in the original paper about the hobbit’s discovery, the researchers proposed that a
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group of Homo erectus somehow got stuck on Flores, and they eventually evolved into a
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new species: the smaller Homo floresiensis.
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And, Flores wouldn’t have been a terrible place to be stranded.
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Today, it’s a forested tropical island, and it seems to have been pretty similar,
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if more variable, while Homo floresiensis was around.
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Now, it’s not clear whether the hobbits actually lived in the cave where their remains
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were found.
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But, based on the number of animal bones and stone tools found in different layers of the
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site, they seem to have used the cave more when the environment was wetter, and less
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when it was drier and less forested.
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And the hobbits seem to have had a rather … exotic diet, at least by our standards.
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The animal remains found in the cave include a lot of very young pygmy Stegodon, an elephant
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relative that, like the hobbits, seems to have evolved into a smaller version of its
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mainland cousins.
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A number of these bones have cut-marks on them, and some are even burned, so Homo floresiensis
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seems to have been able to use fire.
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And there were also lots of bones of Komodo dragons, which are still formidable predators
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today.
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It’s not clear whether the hobbits were hunting the Komodo dragons or just scavenging
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them - but it’s possible that the hobbits might have been hunted by the dragons!
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Interestingly enough, there don’t seem to be any bones of adult pygmy Stegodon in the
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cave, which suggests that the hobbits might not have been able to take down a full-grown
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elephant.
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The hobbits also left behind a number of simple stone tools, like cores, flakes, and points,
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some of which seem to have been used not only for hunting, but also for processing plant
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materials.
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But other experts weren’t convinced that these artifacts had been made by a new species
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of hominin.
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Instead, they thought the so-called hobbits were actually modern Homo sapiens, but from
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a population of very small-bodied people, like some groups of tropical hunter-gatherers
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today.
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And, they argued, LB1 likely had some kind of pathological condition.
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To support their case, these researchers compared the bones from LB1 with the skeletons of various
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indigenous peoples of Indonesia and Australia.
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Their thinking was that the best populations to compare them to would be ones that lived
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in the same region and environments as the hobbit.
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And, they said, more than 140 features of LB1’s skull matched those of modern humans
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from the area.
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But the researchers who thought Homo floresiensis was a new species countered this argument.
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They said that there are a number of groups of people from around the world who have adapted
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to their environments by becoming smaller - but none of them ended up with the same
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tiny brain and odd limb proportions as the hobbit.
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So that just left the claim that LB1 was an individual with some kind of pathological
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condition.
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In a series of papers, the supporters of this hypothesis proposed a number of different
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conditions that might explain LB1’s very small skull, short stature, and other features.
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These included Laron Syndrome, which is caused by an insensitivity to certain growth hormones,
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as well as microcephaly, or having a much smaller-than-average head circumference, and
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Down Syndrome.
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And every time, the scientists who thought Homo floresiensis was a new species pointed
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out that none of the proposed disorders quite matched LB1’s anatomy.
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Plus they didn’t explain all of the hobbit’s features that resembled those of older hominins,
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like its archaic-looking wrist bones.
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The two camps went back and forth, publishing paper after paper, questioning each other’s
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arguments - and not always in civil terms.
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And while one group of researchers still thinks LB1 is a pathological modern human, some recent
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work has suggested a third theory of where the hobbits came from.
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The Shire!
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No, just kidding
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Instead of being a dwarfed version of Homo erectus, or a modern human with a developmental
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disorder, maybe the hobbit actually evolved from another, earlier hominin species -- one
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we don’t know about yet.
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In this scenario, Homo floresiensis is still its own, new species, but its ancestor wasn’t
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Homo erectus.
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And in 2017, some experts tested this hypothesis.
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They collected a whole lot of skeletal data from 11 different hominin species, and built
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two kinds of evolutionary trees that showed how the species might be related.
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One tree was designed around the notion of parsimony, the idea that the simplest path
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for one species to diverge into another is the one with the fewest changes in features.
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The other model was built using statistics, analyzing how likely a path might be, based
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on different models of evolutionary change.
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And both methods came up with pretty similar results.
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In one scenario, Homo floresiensis shared a common ancestor with Homo habilis, a hominin
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that lived in Africa between 2.4 million and 1.4 million years ago.
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In the other scenario, the hobbits are part of the sister group to the branch that includes
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Homo habilis, Homo erectus, and us.
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What all this suggests is that Homo erectus might not have been the first hominin to leave
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Africa - even though that’s what the current fossil record shows.
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It also suggests that there’s probably a lot of ancestors on the hobbit’s branch
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of the family tree that are still out there, waiting to be found.
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Which is amazing even to think about, there’s so much we don’t know!
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Now where does the debate about the hobbit stand today?
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Well, the consensus among most experts is that Homo floresiensis is probably its own,
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unique species.
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This was helped along by the publication of revised dates for the bones and stone artifacts
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that were found in the cave.
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Instead of the dating to between 35,000 and 14,000 years ago, as we first thought, the
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deposit that the skeleton came from was more like 100,000 to 60,000 years old.
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And the stone artifacts were between 190,000 and 50,000 years old.
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So the odd little skeleton was older than we originally thought, which made its archaic-looking
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anatomy somewhat easier to understand.
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And it looks like there were changes in the island’s climate and volcanic eruptions
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around 50,000 years ago, which might explain why the species disappeared.
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But who it’s descended from is still a wide-open question.
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And the more digging we do in Southeast Asia, the more complicated our evolutionary story
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seems to be.
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For example, in 2019, scientists working in the Philippines announced their discovery
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of teeth and bones from a new species of hominin dated to about 50,000 to 67,000 years old.
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It was named Homo luzonensis, and it overlapped in time with the hobbits and us, along with
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some of our other extinct relatives.
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And it had a different mix of ancient and modern features than the hobbit, like very
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small molars but with larger premolars, and curved finger bones.
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This discovery -- of another new hominin on a remote island in Southeast Asia-- just reinforces
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how much more we have to learn about our family tree.
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Excavations at the cave where the original hobbit was found are on-going.
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And anthropologists are trying all the latest genetic techniques to try to unravel the mystery
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of the hobbit at the molecular level.
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But so far, our attempts to extract DNA from the hobbit’s bones have failed, because
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hot, humid caves are just terrible for preserving DNA.
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But even newer methods, like extracting ancient proteins, like collagen, from the bones have
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yet to be tried.
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So maybe there’s still some hope for figuring out where Homo floresiensis fits into our
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family tree.
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And maybe that will help us better understand this particular chapter of human evolution,
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back in the time when hobbits were real.
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