20:26
TED2003

Deborah Gordon: The emergent genius of ant colonies

デボラ・ゴードンのアリにかける情熱

Filmed:

砂まみれのショベルカーと日本製ペイントマーカー、そして数人の学生を従えて、デボラ・ゴードンがアリゾナ砂漠のアリコロニーを掘り起こし、アリの複雑な世界を探究します。

- Ecologist
By studying how ant colonies work without any one leader, Deborah Gordon has identified striking similarities in how ant colonies, brains, cells and computer networks regulate themselves. Full bio

I study ants, and that's because I like to think about how organizations work.
組織がいかに作用するのかを見るのが好きなので アリの研究をしています
00:13
And in particular, how the simple parts of organizations
いかにして 単純な部分同士の相互作用から
00:18
interact to create the behavior of the whole organization.
全体の習性が生じるのか見るのが好きです
00:24
So, ant colonies are a good example of an organization like that,
ですからアリコロニーはそのような組織の良い例なのです
00:29
and there are many others. The web is one.
インターネットもその一例だと言えますし
00:35
There are many biological systems like that --
脳 細胞 発達中の受精卵のような
00:37
brains, cells, developing embryos.
生物学的システムもたくさんあります
00:39
There are about 10,000 species of ants.
アリは約一万種います
00:42
They all live in colonies consisting of one or a few queens,
どのアリも女王アリ1匹もしくは数匹がいるアリコロニーに住んでいて
00:45
and then all the ants you see walking around are sterile female workers.
外で見かけるアリはどれも産卵しない雌アリです
00:50
And all ant colonies have in common that there's no central control.
どのアリコロニーにも共通するのは中央制御が存在せず
00:55
Nobody tells anybody what to do.
指揮監督がいません
00:59
The queen just lays the eggs. There's no management.
女王アリが産卵するだけで 管理者はいません
01:01
No ant directs the behavior of any other ant.
アリの行動を監督するアリはいなのです
01:05
And I try to figure out how that works.
私はその仕組みを解明しようとしています
01:09
And I've been working for the past 20 years
過去20年間 アリゾナ州南東に生息する―
01:13
on a population of seed-eating ants in southeastern Arizona.
種を食べるアリの個体群を研究しています
01:15
Here's my study site. This is really a picture of ants,
これが研究場所で アリの写真ですが
01:19
and the rabbit just happens to be there.
たまたまウサギが写っています
01:21
And these ants are called harvester ants because they eat seeds.
このアリが収穫アリと呼ばれるのは種を食べるからです
01:25
This is the nest of the mature colony, and there's the nest entrance.
これは成長したコロニーの巣と巣の入口です
01:29
And they forage maybe for about 20 meters away,
アリは20mほど先まで食糧を探しに行き
01:33
gather up the seeds and bring them back to the nest, and store them.
種を集めて巣に持ち帰り 貯えます
01:36
And every year I go there and make a map of my study site.
私は毎年ここに行き 研究場所の地図を作成しています
01:40
This is just a road. And it's not very big:
これはただの道路で 広さは
01:42
it's about 250 meters on one side, 400 on the other.
だいたい縦250m 横400mです
01:45
And every colony has a name, which is a number,
どのコロニーにも識別番号をつけ
01:48
which is painted on a rock. And I go there every year
石に書いておきます
01:50
and look for all the colonies that were alive the year before,
毎年 死んだコロニーを調べ
01:53
and figure out which ones have died, and put all the new ones on the map.
新しく出来た巣は地図に追加します
01:56
And by doing this I know how old they all are.
こうすることでコロニーの年数を把握します
02:00
And because of that, I've been able to study how their behavior changes
その結果 コロニーの成長につれて
02:02
as the colony gets older and larger.
彼らの行動の変化を研究することが出来るのです
02:06
So I want to tell you about the life cycle of a colony.
コロニーのライフサイクルを説明します
02:09
Ants never make more ants; colonies make more colonies.
着目すべきは個々のアリではなく 組織として働くコロニーです
02:11
And they do that by each year sending out the reproductives --
毎年 羽のある繁殖アリを交尾飛行へと
02:15
those are the ones with wings -- on a mating flight.
送りだすことで繁殖させます
02:18
So every year, on the same day -- and it's a mystery exactly how that happens --
いかに起きるかは謎ですが毎年同じ日に
02:22
each colony sends out its virgin, unmated queens with wings, and the males,
どのコロニーも羽のある処女女王アリと雄アリを送りだし
02:26
and they all fly to a common place. And they mate.
みんな決まった場所へ飛んで行き 交尾をします
02:32
And this shows a recently virgin queen. Here's her wings.
これは最近の羽のついた処女女王アリです
02:36
And she's in the process of mating with this male,
女王アリは雄アリと交尾中で
02:42
and there's another male on top waiting his turn.
別の雄アリが2匹の上で順番を待っています
02:47
Often the queens mate more than once.
女王アリはたいてい2回以上交尾をして
02:50
And after that, the males all die. That's it for them.
交尾後 雄アリは全て死にます ご苦労さま
02:52
(Laughter)
(笑)
02:55
And then the newly mated queens fly off somewhere, drop their wings,
交尾をした女王アリは別の場所へと飛び 羽を落とし
02:57
dig a hole and go into that hole and start laying eggs.
穴を掘って中へ入り 産卵し始めます
03:02
And they will live for 15 or 20 years, continuing to lay eggs
女王アリは交尾の際に蓄えた精子を使って産卵し続け
03:06
using the sperm from that original mating.
約15~20年生きます
03:11
So the queen goes down in there.
女王アリは地中に入り
03:14
She lays eggs, she feeds the larvae -- so an ant starts as an egg, then it's a larva.
卵を産んで それが幼虫になると 女王アリは蓄えてある―
03:16
She feeds the larvae by regurgitating from her fat reserves.
脂肪を吐き出して幼虫を育てます
03:21
Then, as soon as the ants -- the first group of ants -- emerge,
そして第一番目のアリ集団が発生するや否や
03:25
they're larvae. Then they're pupae. Then they come out as adult ants.
幼虫 さなぎを経てアリの成虫になります
03:29
They go out, they get the food, they dig the nest,
アリは地上へ上がり 食べ物を得て 巣を掘り
03:32
and the queen never comes out again.
女王は2度と地上に上がりません
03:35
So this is a one-year-old colony -- this happens to be 536.
これは出来てから1年経つコロニー536番です
03:37
There's the nest entrance, there's a pencil for scale.
巣の入口の大きさ比較に鉛筆を置いてあります
03:41
So this is the colony founded by a queen the previous summer.
これは昨夏出来たばかりのコロニーです
03:43
This is a three-year-old colony.
これは3年目のコロニーです
03:47
There's the nest entrance, there's a pencil for scale.
巣の入口の大きさ比較に鉛筆を置いてあります
03:49
They make a midden, a pile of refuse -- mostly the husks of the seeds that they eat.
アリが作るゴミの山は大方が食糧の種の皮です
03:53
This is a five-year-old colony. This is the nest entrance, here's a pencil for scale.
これは5年目のコロニーで 巣の入口の大きさ比較に鉛筆を置いてあります
03:58
This is about as big as they get, about a meter across.
巣は大きくても直径1m程度です
04:03
And then this is how colony size and numbers of worker ants changes --
このグラフはコロニーの大きさを表す働きアリの数が
04:07
so this is about 10,000 worker ants --
コロニーの年数とともにどう変化するかを示します
04:12
changes as a function of colony age, in years.
これは働きアリ約1万匹です
04:15
So it starts out with zero ants, just the founding queen,
最初は女王アリだけで 働きアリ0匹から始まり
04:18
and it grows to a size of about 10 or 12 thousand ants when the colony is five.
5年経つまでに1万~1万2千匹ほどまで増加します
04:23
And it stays that size until the queen dies
その後 15~20歳になった女王アリが
04:27
and there's nobody to make more ants, when she's about 15 or 20 years old.
死んでアリが生まれなくなるまで アリの数は変化しません
04:30
And it's when they reach this stable size, in numbers of ants,
アリの数がここまで安定すると
04:35
that they start to reproduce.
アリは繁殖し始めます
04:39
That is, to send more winged queens and males to that year's mating flight.
羽のある女王アリと雄アリをその年の交尾飛行へと送りだすのです
04:41
And I know how colony size changes as a function of colony age
コロニーの使用年数と大きさの相関関係を把握しているのは
04:47
because I've dug up colonies of known age and counted all the ants. (Laughter)
使用年数が確実なコロニーを掘り起こし すべてのアリを数えたからです
04:52
So that's not the most fun part of this research, although it's interesting.
興味深いんですが この研究で一番楽しい部分とは言えません
04:59
(Laughter)
(笑)
05:04
Really the question that I think about with these ants is what I call task allocation.
私が知りたいのは このアリの仕事の割当てです
05:05
That's not just how is the colony organized,
コロニーの組織のされ方ではなく
05:10
but how does it change what it's doing?
いかに動きが変わるのか?
05:13
How is it that the colony manages to adjust
状況の変化と共に 各仕事につく働きアリの数を
05:15
the numbers of workers performing each task as conditions change?
いかにコロニーは調整しているのか?
05:19
So, things happen to an ant colony.
色々なことが考えられます
05:23
When it rains in the summer, it floods in the desert.
夏の雨で砂漠が氾濫すれば
05:25
There's a lot of damage to the nest,
巣には大きな被害が出て
05:28
and extra ants are needed to clean up that mess.
後片付けをするアリが余分に必要となります
05:30
When extra food becomes available --
たくさん食糧が調達できる時は
05:33
and this is what everybody knows about picnics --
ピクニックでよく見かけるように
05:35
then extra ants are allocated to collect the food.
食糧収集にいつも以上のアリが配置されます
05:37
So, with nobody telling anybody what to do, how is it that
指揮監督なしで いかにコロニーでは
05:40
the colony manages to adjust the numbers of workers performing each task?
各仕事に就くアリの数を調整するのでしょう?
05:43
And that's the process that I call task allocation.
これは私が仕事分配と呼んでいる過程です
05:47
And in harvester ants, I divide the tasks
巣の外で見かける
05:51
of the ants I see just outside the nest
アリの仕事を
05:53
into these four categories: where an ant is foraging,
4種に分類しました
05:55
when it's out along the foraging trail, searching for food or bringing food back.
外で食糧を調達してくる食糧アリ
05:58
The patrollers -- that's supposed to be a magnifying glass --
虫メガネを持っている偵察アリは
06:03
are an interesting group that go out early in the morning
食糧アリの活動前に
06:06
before the foragers are active.
早朝から動きだす面白い集団です
06:08
They somehow choose the direction that the foragers will go,
どういうわけか 偵察アリは食糧アリが行く方向を決め
06:10
and by coming back -- just by making it back --
その方向から無事に帰ってくることで
06:13
they tell the foragers that it's safe to go out.
外出しても安全だと食糧アリに教えます
06:16
Then the nest maintenance workers work inside the nest,
整備アリは巣の中で働きます
06:19
and I wanted to say that the nests look a lot like Bill Lishman's house.
巣はビル リシュマンの家にそっくりです
06:22
That is, that there are chambers inside,
と言うのも 中に小室があって
06:27
they line the walls of the chambers with moist soil
湿った土で小室の壁を覆うと
06:29
and it dries to a kind of an adobe-like surface in it.
日干し煉瓦のように乾きます
06:33
It also looks very similar to some of the cave dwellings
この地域に見られるホピ族の
06:36
of the Hopi people that are in that area.
洞窟住居にも類似しています
06:39
And the nest maintenance workers do that inside the nest,
整備アリは巣の中をそのように施し
06:42
and then they come out of the nest carrying bits of dry soil in their mandibles.
大あごで乾いた土を地上に運びます
06:46
So you see the nest maintenance workers come out with a bit of sand,
砂を持って出てくる整備アリは
06:49
put it down, turn around, and go back in.
砂を置き 方向転換して 戻ります
06:52
And finally, the midden workers put some kind of territorial chemical in the garbage.
最後に ごみアリは ある縄張り物質をゴミにつけます
06:54
So what you see the midden workers doing is making a pile of refuse.
ごみアリはゴミの山を作るんです
07:02
On one day, it'll all be here, and then the next day
その日によって違った場所に
07:05
they'll move it over there, and then they'll move it back.
ゴミの山を作りだします
07:07
So that's what the midden workers do.
それがごみアリの仕事です
07:09
And these four groups are just the ants outside the nest.
この4つのグループは巣の外で仕事をするアリで
07:13
So that's only about 25 percent of the colony, and they're the oldest ants.
全体のわずか25%で 最年長アリです
07:17
So, an ant starts out somewhere near the queen.
どのアリも女王アリの近くから出てきたわけです
07:21
And when we dig up nests we find they're about as deep
掘り起こすと 巣はコロニーの幅ほどの深さがあり
07:24
as the colony is wide, so about a meter deep for the big old nests.
大きくて古い巣は深さが1mほどあります
07:27
And then there's another long tunnel and a chamber, where we often find the queen,
つるはしで岩を8時間叩き割って行くと
07:31
after eight hours of hacking away at the rock with pickaxes.
長い通路の奥の小部屋に女王アリを見つけます
07:36
I don't think that chamber has evolved because of me and my backhoe
我々がショベルカーやつるはしで掘り起こした為に
07:40
and my crew of students with pickaxes,
小室がこの形になったとは思いません
07:44
but instead because when there's flooding,
時々起こる洪水のため
07:46
occasionally the colony has to go down deep.
コロニーは深さがなくてはいけません
07:48
So there's this whole network of chambers.
それで これほどまでの小室があるのです
07:51
The queen's in there somewhere; she just lays eggs.
女王アリはどこかで産卵だけしています
07:53
There's the larvae, and they consume most of the food.
幼虫は食糧のほとんどを消費します
07:56
And this is true of most ants --
ほとんどのアリに共通していることですが
07:59
that the ants you see walking around don't do much eating.
外で見かけるアリはあまり食べることをしません
08:01
They bring it back and feed it to the larvae.
食糧を調達し幼虫に餌付けします
08:03
When the foragers come in with food, they just drop it into the upper chamber,
食糧アリが食糧を持ってくると上部の小室へと投げ込みます
08:05
and other ants come up from below, get the food,
下から別のアリがやってきて食糧を受け取り
08:10
bring it back, husk the seeds, and pile them up.
運んで種の皮をむき 積み上げます
08:13
There are nest maintenance workers working throughout the nest.
整備アリは巣の至る所で働いています
08:16
And curiously, and interestingly, it looks as though at any time
面白いことに どんな時も コロニーにいるアリの約半分は
08:19
about half the ants in the colony are just doing nothing.
何もしていないかのように見えるのです
08:24
So, despite what it says in the Bible,
聖書には “怠け者よ
08:27
about, you know, "Look to the ant, thou sluggard,"
アリのところに行ってみよ” とありますが
08:29
in fact, you could think of those ants as reserves.
このようなアリは補欠選手と考えてもいいでしょう
08:33
That is to say, if something happened -- and I've never seen anything like this happen,
私の20年の研究では見たことがありませんが
08:36
but I've only been looking for 20 years --
いざという時には
08:39
if something happened, they might all come out if they were needed.
全てのアリが出てくるかも知れません
08:41
But in fact, mostly they're just hanging around in there.
でも 大抵その辺でうろついているだけです
08:45
And I think it's a very interesting question --
私が興味を惹かれるのは
08:47
what is there about the way the colony is organized
何もしていないアリの予備軍に何か役割を出しうる
08:49
that might give some function to a reserve of ants who are doing nothing?
コロニーの組織のされ方とは何なのか?
08:52
And they sort of stand as a buffer in between
何もしないアリは巣の奥深くで働くアリと
08:59
the ants working deep inside the nest and the ants working outside.
外で働くアリの調停者のような立場にいます
09:03
And if you mark ants that are working outside, and dig up a colony,
外で働くアリに印をつけてコロニーを掘ると
09:06
you never see them deep down.
絶対に彼らを巣の奥で見かけません
09:10
So what's happening is that the ants work inside the nest when they're younger.
と言うのもアリは若い時に巣の中で働くのです
09:12
They somehow get into this reserve.
いつの間にか この補欠組に入り
09:17
And then eventually they get recruited to join this exterior workforce.
ついには外で働くアリとなります
09:19
And once they belong to the ants that work outside, they never go back down.
一度外で働くようになると地中には戻りません
09:23
Now ants -- most ants, including these, don't see very well.
大方のアリは目がよく見えません
09:28
They have eyes, they can distinguish between light and dark,
明暗を見分けられる程度の目で
09:31
but they mostly work by smell.
ほとんどを嗅覚に頼っています
09:34
So just to reinforce that what you might have thought
ですから女王アリが指揮していると思われたら
09:36
about ant queens isn't true --
それは違います
09:40
you know, even if the queen did have the intelligence
女王アリがアリ全体に指令を出せる―
09:42
to send chemical messages through this whole network of chambers
化学的なメッセージを送る知能を持っていたとしても
09:45
to tell the ants outside what to do,
そんなメッセージで
09:49
there is no way that such messages could make it in time to see
適切なタイミングに働きアリの仕事割り当ての
09:51
the shifts in the allocation of workers that we actually see outside the nest.
変更を届けられることは絶対にあり得ないので
09:55
So that's one way that we know the queen isn't directing the behavior of the colony.
女王はコロニーの動きを指揮していないと分かるのです
10:00
So when I first set out to work on task allocation,
仕事分配の研究を始めたとき
10:05
my first question was, "What's the relationship
最初の疑問は “別の仕事をするアリ同士の
10:08
between the ants doing different tasks?
関係はどうなっているか” でした
10:11
Does it matter to the foragers what the nest maintenance workers are doing?
食糧アリにとって整備アリが何をしているのか問題なのか?
10:14
Does it matter to the midden workers what the patrollers are doing?"
ごみアリにとって偵察アリが何をしているのか問題なのか?
10:17
And I was working in the context of a view of ant colonies in which each ant
生まれてからずっと自分の仕事に徹し 流れ作業における
10:20
was somehow dedicated to its task from birth
自分の位置は知っていても
10:26
and sort of performed independently of the others,
他のアリとは独立して作業しているという見方で
10:29
knowing its place on the assembly line.
研究をしていました
10:32
And instead I wanted to ask, "How are the different task groups interdependent?"
その代わりに異なるグループ間の依存関係を問う事にしました
10:34
So I did experiments where I changed one thing.
条件を一つ変えて実験をしてみました
10:38
So for example, I created more work for the nest maintenance workers
例えば 整備アリが活動をし始める朝早くに
10:40
by putting out a pile of toothpicks near the nest entrance,
巣の入口近くに楊枝を積み上げて
10:44
early in the morning when the nest maintenance workers are first active.
整備アリの仕事を増やしてみました
10:48
This is what it looks like about 20 minutes later.
約20分後にはこのようになり
10:52
Here it is about 40 minutes later.
約40分後にはこのようになりました
10:54
And the nest maintenance workers just take all the toothpicks
整備アリは楊枝を巣の端に運び
10:56
to the outer edge of the nest mound and leave them there.
そこに放置するのです
10:58
And what I wanted to know was, "OK,
それで次に浮かんだ疑問は
11:01
here's a situation where extra nest maintenance workers were recruited --
いつも以上の整備アリが召集された場合
11:04
is this going to have any effect on the workers performing other tasks?"
別の仕事をしているアリに影響は出るのか?
11:07
Then we repeated all those experiments with the ants marked.
印をつけたアリで再度実験を行いました
11:11
So here's some blue nest maintenance workers.
青く印をつけた整備アリです
11:15
And lately we've gotten more sophisticated
最近は以前より凝って
11:18
and we have this three-color system.
3色使っています
11:20
And we can mark them individually so we know which ant is which.
1匹ずつ印をつけるので個体が識別できます
11:22
We started out with model airplane paint
最初はプラモデル用のペンを
11:25
and then we found these wonderful little Japanese markers,
使いましたが その後 日本製の
11:27
and they work really well.
優れたペンを見つけました
11:29
And so just to summarize the result,
結果はと言うと
11:31
well it turns out that yes, the different tasks are interdependent.
異なる仕事は互いに関係があり
11:33
So, if I change the numbers performing one task,
ある仕事をしているアリの数を変えれば
11:36
it changes the numbers performing another.
別の仕事をするアリの数も変わります
11:39
So for example, if I make a mess
例えば 私が何か散らかして
11:41
that the nest maintenance workers have to clean up,
整備アリの仕事量を増やせば
11:43
then I see fewer ants out foraging.
食糧アリは見かけなくなりました
11:45
And this was true for all the pair-wise combinations of tasks.
これはすべての仕事に共通していました
11:47
And the second result, which was surprising to a lot of people,
多くの人を驚かせた2つ目の結果は
11:50
was that ants actually switch tasks.
アリが役割を切り替えることです
11:55
The same ant doesn't do the same task over and over its whole life.
アリは一生を通じて同じ仕事はしません
11:57
So for example, if I put out extra food, everybody else --
例えば 余分な食糧を置いてみると
12:01
the midden workers stop doing midden work and go get the food,
ごみアリはごみ収集を止め食糧調達に行き
12:04
they become foragers.
食糧アリと化します
12:06
The nest maintenance workers become foragers.
整備アリが食糧アリとなり
12:08
The patrollers become foragers.
偵察アリが食糧アリになります
12:10
But not every transition is possible. And this shows how it works.
全ての役割変換が可能なわけではありません
12:12
Like I just said, if there is more food to collect, the patrollers, the midden workers,
先ほどのように 食糧があれば 偵察アリもごみアリも
12:16
the nest maintenance workers will all change to forage.
整備アリも食糧アリに替わります
12:20
If there's more patrolling to do --
障害を作ることで
12:22
so I created a disturbance, so extra patrollers were needed --
通常よりも偵察が必要ならば
12:24
the nest maintenance workers will switch to patrol.
整備アリは偵察アリに替わります
12:28
But if more nest maintenance work is needed --
しかし 楊枝を積み上げて
12:30
for example, if I put out a bunch of toothpicks --
整備の仕事を増やしても
12:33
then nobody will ever switch back to nest maintenance,
整備アリに戻るアリはおらず
12:35
they have to get nest maintenance workers from inside the nest.
巣の中から整備アリを召集しなくてはいけません
12:38
So foraging acts as a sink, and the ants inside the nest act as a source.
巣の中のアリからスタートして 食糧探しがゴールです
12:41
And finally, it looks like each ant is deciding
最後に アリが活動するかどうかは
12:48
moment to moment whether to be active or not.
その時々で決めているようです
12:50
So, for example, when there's extra nest maintenance work to do,
例えば 整備の仕事が増えても
12:53
it's not that the foragers switch over. I know that they don't do that.
食糧アリは仕事を切り替えずに
12:57
But the foragers somehow decide not to come out.
巣から出てきません
13:01
And here was the most intriguing result: the task allocation.
一番興味深い結果だったのは仕事分担です
13:03
This process changes with colony age, and it changes like this.
この過程はコロニーの古さと共に変化します
13:07
When I do these experiments with older colonies --
5年から10年経過した―
13:11
so ones that are five years or older --
古めのコロニーで実験をすると
13:14
they're much more consistent from one time to another
一貫性がより強く見られ恒常的です
13:16
and much more homeostatic. The worse things get,
状況が悪化するほど
13:19
the more I hassle them, the more they act like undisturbed colonies.
せかされるほど 平静を装います
13:21
Whereas the young, small colonies --
それに対し 新しくて小さな
13:24
the two-year-old colonies of just 2,000 ants -- are much more variable.
二千匹いる2年目のコロニーはもっと変わりやすいのです
13:26
And the amazing thing about this is that an ant lives only a year.
驚くのはアリの寿命がわずか1年であること
13:30
It could be this year, or this year.
いつ生まれても1年です
13:35
So, the ants in the older colony that seem to be more stable
古めのコロニーの落ち着いて見えるアリは
13:37
are not any older than the ants in the younger colony.
新しいコロニーにいるアリより年上という訳ではないのです
13:41
It's not due to the experience of older, wiser ants.
年の功ではありません
13:44
Instead, something about the organization
その代わりに組織に関わる何かが
13:47
must be changing as the colony gets older.
コロニーが古くなるにつれて変わるに違いありません
13:49
And the obvious thing that's changing is its size.
明らかに変化しているのはコロニーの大きさです
13:52
So since I've had this result, I've spent a lot of time trying to figure out
この結果を得てから 全体を見れるアリがいないことを踏まえて
13:55
what kinds of decision rules -- very simple, local, probably olfactory, chemical
単純で 局所的で おそらく嗅覚に関わり 化学的で
14:01
rules could an ant could be using, since no ant can assess the global situation --
観察可能なアリの決断規則を
14:07
that would have the outcome that I see,
突きとめようと時間をかけてきました
14:12
these predictable dynamics, in who does what task.
誰がどの仕事をするのか予測できる過程
14:15
And it would change as the colony gets larger.
そしてそれはコロニーの老化と共に変化します
14:18
And what I've found out is that ants are using a network of antennal contact.
私が発見したのは アリは触角を使った連絡網を使っていることです
14:21
So anybody who's ever looked at ants has seen them touch antennae.
アリを観察したことのある方なら知っているでしょう
14:28
They smell with their antennae.
アリは触角で匂いをかぎ分けます
14:31
When one ant touches another, it's smelling it,
アリがアリを触るのは 匂いを嗅いでいるのです
14:33
and it can tell, for example, whether the other ant is a nest mate
同じ巣の仲間かどうか確認できるのです
14:35
because ants cover themselves and each other, through grooming,
コロニー独自の匂いがする油の層で
14:39
with a layer of grease, which carries a colony-specific odor.
お互いにグルーミングして体を覆います
14:43
And what we're learning is that an ant uses the pattern of its antennal contacts,
今わかって来ているのはアリは触角接触のパターンを使い
14:47
the rate at which it meets ants of other tasks, in deciding what to do.
他の仕事担当のアリと会う割合で何をするのか決めています
14:52
And so what the message is, is not any message
アリからアリへのメッセージではなく
14:57
that they transmit from one ant to another, but the pattern.
パターンがあるのです
15:00
The pattern itself is the message.
パターン自体がメッセージです
15:04
And I'll tell you a little bit more about that.
後からまた説明しますが
15:06
But first you might be wondering:
アリはいかに自分の役割が
15:08
how is it that an ant can tell, for example, I'm a forager.
わかるのでしょう 例えば自分が食糧アリならば
15:10
I expect to meet another forager every so often.
他の食糧アリと頻繁に会うはずです
15:15
But if instead I start to meet a higher number of nest maintenance workers,
その代わりに沢山の整備アリと会ったら
15:17
I'm less likely to forage.
おそらく食糧探しには行きません
15:21
So it has to know the difference between
そうなると食糧アリと整備アリの違いを
15:23
a forager and a nest maintenance worker.
見分けなくてはいけないのです
15:25
And we've learned that, in this species --
他の種も同じだと思いますが
15:27
and I suspect in others as well --
この種のアリの体についている―
15:30
these hydrocarbons, this layer of grease on the outside of ants,
油の層の炭化水素は
15:33
is different as ants perform different tasks.
仕事により異なることがわかりました
15:37
And we've done experiments that show that
実験でわかったのは
15:40
that's because the longer an ant stays outside,
アリが外にいる時間が長くなるほど
15:42
the more these simple hydrocarbons on its surface change,
体の表面の単純な炭化水素が変わるので
15:44
and so they come to smell different by doing different tasks.
仕事によって体の匂いも異なるのです
15:48
And they can use that task-specific odor in cuticular hydrocarbons --
仕事ごとに違う匂いを角皮の炭化水素に使えるのです
15:51
they can use that in their brief antennal contacts to somehow
短時間の触角の接触の中で 匂いを使って
15:55
keep track of the rate at which they're meeting ants of certain tasks.
特定の仕事のアリと会う割合を把握します
15:59
And we've just recently demonstrated this
我々は最近 炭化水素の抽出物を
16:03
by putting extract of hydrocarbons on little glass beads,
小さなガラス玉につけ 適切な割合で
16:06
and dropping the beads gently down into the nest entrance at the right rate.
巣の入口にそっと落とすことで証明してみました
16:10
And it turns out that ants will respond to the right rate of contact
そうするとアリは炭化水素つきのガラス玉に
16:14
with a glass bead with hydrocarbon extract on it,
本物のアリと接触するように
16:18
as they would to contact with real ants.
反応することがわかったのです
16:21
So I want now to show you a bit of film --
少し映像をお見せしますが
16:26
and this will start out, first of all, showing you the nest entrance.
まず見えるのは巣の入口部分です
16:33
So the idea is that ants are coming in and out of the nest entrance.
アリが巣に出たり入ったりしています
16:38
They've gone out to do different tasks, and the rate at which they meet
別の仕事をしに出て行きました アリが出入りするときに
16:41
as they come in and out of the nest entrance determines, or influences,
別のアリと会う割合が 外に出るかどうかや
16:46
each ant's decision about whether to go out, and which task to perform.
どの仕事をするかという判断に影響を与えます
16:50
This is taken through a fiber optics microscope. It's down inside the nest.
光ファイバー顕微鏡を使って巣の中を撮影しました
16:54
In the beginning you see the ants
初めに光ファイバー顕微鏡と
16:58
just kind of engaging with the fiber optics microscope.
接触しているのアリが見えます
17:00
But the idea is that the ants are in there,
巣の中のアリはどれも
17:02
and each ant is experiencing a certain flow of ants past it --
すれ違って行くアリを感知し
17:06
a stream of contacts with other ants.
他のアリと接触しています
17:11
And the pattern of these interactions determines
この関わり合いのパターンで
17:14
whether the ant comes back out, and what it does when it comes back out.
アリが外に戻るかどうか そして外でどの仕事をするのかを決めます
17:17
You can also see this in the ants just outside the nest entrance like these.
このような巣のすぐ外にいるアリにも見られることです
17:22
Each ant, then, as it comes back in, is contacting other ants.
どのアリも巣の中に戻ると他のアリと接触しています
17:29
And the ants that are waiting just inside the nest entrance
巣の入り口のすぐ中で待っていたアリは
17:33
to decide whether to go out on their next trip,
入ってくるアリと接触して
17:36
are contacting the ants coming in.
外に出かけるか決めます
17:39
So, what's interesting about this system is that it's messy.
このシステムの面白い部分は乱雑なところです
17:41
It's variable. It's noisy. And, in particular, in two ways.
特に2つの点において可変的で混沌としています
17:45
The first is that the experience of the ant -- of each ant -- can't be very predictable.
一つ目にそれぞれのアリの経験はあまり予測できません
17:50
Because the rate at which ants come back depends on
なぜなら アリは外に出て仕事をする為 アリが戻ってくる割合は
17:55
all the little things that happen to an ant as it goes out and does its task outside.
アリに起きている状況次第だからです
17:58
And the second thing is that an ant's ability to assess this pattern
二つ目は高度な計算が出来るアリはいないので
18:03
must be very crude because no ant can do any sophisticated counting.
このパターンを評価するアリの能力はいい加減に違いないのです
18:08
So, we do a lot of simulation and modeling, and also experimental work,
ですから シミュレーションやモデリングや実験をたくさん行い
18:15
to try to figure out how those two kinds of noise combine to,
その2種類の情報がコロニーの
18:19
in the aggregate, produce the predictable behavior of ant colonies.
予測出来る行動を生み出すのか探究しています
18:25
Again, I don't want to say that this kind of haphazard pattern of interactions
このような偶然の接触パターンが
18:31
produces a factory that works with the precision and efficiency of clockwork.
正確で効率的な時計仕掛けの工場を作るというのではありません
18:36
In fact, if you watch ants at all, you end up trying to help them
実際アリの観察を始めると 彼らがすべきことを
18:43
because they never seem to be doing anything
彼らがしているようには見えないため
18:46
exactly the way that you think that they ought to be doing it.
結局手助けしてしまうことになります
18:48
So it's not really that out of these haphazard contacts, perfection arises.
ですから偶然の接触から完璧な状態が生まれるのではありません
18:51
But it works pretty well.
でも うまく働いています
18:58
Ants have been around for several hundred million years.
アリは数百万年も生きてきた生き物で
19:00
They cover the earth, except for Antarctica.
南極大陸を除き 至る所で生息しています
19:03
Something that they're doing is clearly successful enough
彼らの偶然的な接触のパターンは
19:06
that this pattern of haphazard contacts, in the aggregate,
全体としてアリを繁栄させるのを可能にする―
19:10
produces something that allows ants to make a lot more ants.
何かを可能にしているのです
19:13
And one of the things that we're studying is how natural selection
我々は自然選択がいかにして
19:17
might be acting now to shape this use of interaction patterns --
この相互作用パターンの使用やネットワークを形作るのかに影響し
19:20
this network of interaction patterns --
コロニーの食糧探しの効率化を上げるのに
19:27
to perhaps increase the foraging efficiency of ant colonies.
影響しているかを研究しています
19:29
So the one thing, though, that I want you to remember about this
覚えておいていただきたいのは
19:34
is that these patterns of interactions
この相互作用パターンは
19:37
are something that you'd expect to be closely connected to colony size.
コロニーの大きさと密接に関係していると考えられるということです
19:40
The simplest idea is that when an ant is in a small colony --
一番単純な考えは アリがコロニーの大きさに関係なく
19:45
and an ant in a large colony can use the same rule,
同じルールを使うという考えです
19:50
like "I expect to meet another forager every three seconds."
例えば “3秒毎に食糧アリと会う” と予測しても
19:54
But in a small colony, it's likely to meet fewer foragers,
小さいコロニーで それほど食糧アリに会いません
19:58
just because there are fewer other foragers there to meet.
食糧アリの数が少ないからなのです
20:01
So this is the kind of rule that, as the colony develops and gets older and larger,
この種のルールがあれば コロニーが成長するにつれて
20:05
will produce different behavior in an old colony and a small young one.
異なる行動が生み出されます
20:11
Thank you.
ありがとうございました
20:16
(Applause)
(拍手)
20:18
Translated by Takako Sato
Reviewed by Natsuhiko Mizutani

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About the Speaker:

Deborah Gordon - Ecologist
By studying how ant colonies work without any one leader, Deborah Gordon has identified striking similarities in how ant colonies, brains, cells and computer networks regulate themselves.

Why you should listen

Ecologist Deborah M. Gordon has learned that ant colonies can work without central control by using simple interactions like how often the insects touch antennae. Contrary to the notion that colonies are organized by efficient ants, she has instead discovered that evolution has produced “noisy” systems that tolerate accident and respond flexibly to the environment. When conditions are tough, natural selection favors colonies that conserve resources.

Her studies of ant colonies have led her and her Stanford colleagues to the discovery of the “Anternet,” which regulates foraging in ants in the same way the internet regulates data traffic. But as she said to Wired in 2013, "Insect behavior mimicking human networks ... is actually not what’s most interesting about ant networks. What’s far more interesting are the parallels in the other direction: What have the ants worked out that we humans haven’t thought of yet?" Her latest exploration: How do ants behave in space?

More profile about the speaker
Deborah Gordon | Speaker | TED.com