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:
Readability: 3.5
1,170,189 views
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。
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. Full bio
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
Double-click the English transcript below to play the video.
00:13
I study ants, and that's because I like to think about how organizations work.
0
1000
5000
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
00:18
And in particular, how the simple parts of organizations
1
6000
6000
いかにして 単純な部分同士の相互作用から
00:24
interact to create the behavior of the whole organization.
2
12000
4000
全体の習性が生じるのか見るのが好きです
00:29
So, ant colonies are a good example of an organization like that,
3
17000
6000
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
00:35
and there are many others. The web is one.
4
23000
2000
インターネットもその一例だと言えますし
00:37
There are many biological systems like that --
5
25000
2000
脳 細胞 発達中の受精卵のような
00:39
brains, cells, developing embryos.
6
27000
3000
生物学的システムもたくさんあります
00:42
There are about 10,000 species of ants.
7
30000
3000
アリは約一万種います
00:45
They all live in colonies consisting of one or a few queens,
8
33000
5000
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
00:50
and then all the ants you see walking around are sterile female workers.
9
38000
5000
外で見かけるアリはどれも産卵しない雌アリです
00:55
And all ant colonies have in common that there's no central control.
10
43000
4000
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
00:59
Nobody tells anybody what to do.
11
47000
2000
指揮監督がいません
01:01
The queen just lays the eggs. There's no management.
12
49000
4000
女王アリが産卵するだけで 管理者はいません
01:05
No ant directs the behavior of any other ant.
13
53000
4000
アリの行動を監督するアリはいなのです
01:09
And I try to figure out how that works.
14
57000
2000
私はその仕組みを解明しようとしています
01:13
And I've been working for the past 20 years
15
61000
2000
過去20年間 アリゾナ州南東に生息する―
01:15
on a population of seed-eating ants in southeastern Arizona.
16
63000
4000
種を食べるアリの個体群を研究しています
01:19
Here's my study site. This is really a picture of ants,
17
67000
2000
これが研究場所で アリの写真ですが
01:21
and the rabbit just happens to be there.
18
69000
3000
たまたまウサギが写っています
01:25
And these ants are called harvester ants because they eat seeds.
19
73000
4000
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
01:29
This is the nest of the mature colony, and there's the nest entrance.
20
77000
4000
これは成長したコロニーの巣と巣の入口です
01:33
And they forage maybe for about 20 meters away,
21
81000
3000
アリは20mほど先まで食糧を探しに行き
01:36
gather up the seeds and bring them back to the nest, and store them.
22
84000
4000
種を集めて巣に持ち帰り 貯えます
01:40
And every year I go there and make a map of my study site.
23
88000
2000
私は毎年ここに行き 研究場所の地図を作成しています
01:42
This is just a road. And it's not very big:
24
90000
3000
これはただの道路で 広さは
01:45
it's about 250 meters on one side, 400 on the other.
25
93000
3000
だいたい縦250m 横400mです
01:48
And every colony has a name, which is a number,
26
96000
2000
どのコロニーにも識別番号をつけ
01:50
which is painted on a rock. And I go there every year
27
98000
3000
石に書いておきます
01:53
and look for all the colonies that were alive the year before,
28
101000
3000
毎年 死んだコロニーを調べ
01:56
and figure out which ones have died, and put all the new ones on the map.
29
104000
4000
新しく出来た巣は地図に追加します
02:00
And by doing this I know how old they all are.
30
108000
2000
こうすることでコロニーの年数を把握します
02:02
And because of that, I've been able to study how their behavior changes
31
110000
4000
その結果 コロニーの成長につれて
02:06
as the colony gets older and larger.
32
114000
3000
彼らの行動の変化を研究することが出来るのです
02:09
So I want to tell you about the life cycle of a colony.
33
117000
2000
コロニーのライフサイクルを説明します
02:11
Ants never make more ants; colonies make more colonies.
34
119000
4000
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
02:15
And they do that by each year sending out the reproductives --
35
123000
3000
毎年 羽のある繁殖アリを交尾飛行へと
02:18
those are the ones with wings -- on a mating flight.
36
126000
3000
送りだすことで繁殖させます
02:22
So every year, on the same day -- and it's a mystery exactly how that happens --
37
130000
4000
いかに起きるかは謎ですが毎年同じ日に
02:26
each colony sends out its virgin, unmated queens with wings, and the males,
38
134000
6000
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
02:32
and they all fly to a common place. And they mate.
39
140000
4000
みんな決まった場所へ飛んで行き 交尾をします
02:36
And this shows a recently virgin queen. Here's her wings.
40
144000
6000
これは最近の羽のついた処女女王アリです
02:42
And she's in the process of mating with this male,
41
150000
4000
女王アリは雄アリと交尾中で
02:47
and there's another male on top waiting his turn.
42
155000
3000
別の雄アリが2匹の上で順番を待っています
02:50
Often the queens mate more than once.
43
158000
2000
女王アリはたいてい2回以上交尾をして
02:52
And after that, the males all die. That's it for them.
44
160000
3000
交尾後 雄アリは全て死にます ご苦労さま
02:55
(Laughter)
45
163000
2000
（笑）
02:57
And then the newly mated queens fly off somewhere, drop their wings,
46
165000
5000
交尾をした女王アリは別の場所へと飛び 羽を落とし
03:02
dig a hole and go into that hole and start laying eggs.
47
170000
4000
穴を掘って中へ入り 産卵し始めます
03:06
And they will live for 15 or 20 years, continuing to lay eggs
48
174000
5000
女王アリは交尾の際に蓄えた精子を使って産卵し続け
03:11
using the sperm from that original mating.
49
179000
2000
約15~20年生きます
03:14
So the queen goes down in there.
50
182000
2000
女王アリは地中に入り
03:16
She lays eggs, she feeds the larvae -- so an ant starts as an egg, then it's a larva.
51
184000
5000
卵を産んで それが幼虫になると 女王アリは蓄えてある―
03:21
She feeds the larvae by regurgitating from her fat reserves.
52
189000
4000
脂肪を吐き出して幼虫を育てます
03:25
Then, as soon as the ants -- the first group of ants -- emerge,
53
193000
4000
そして第一番目のアリ集団が発生するや否や
03:29
they're larvae. Then they're pupae. Then they come out as adult ants.
54
197000
3000
幼虫 さなぎを経てアリの成虫になります
03:32
They go out, they get the food, they dig the nest,
55
200000
3000
アリは地上へ上がり 食べ物を得て 巣を掘り
03:35
and the queen never comes out again.
56
203000
2000
女王は2度と地上に上がりません
03:37
So this is a one-year-old colony -- this happens to be 536.
57
205000
4000
これは出来てから1年経つコロニー536番です
03:41
There's the nest entrance, there's a pencil for scale.
58
209000
2000
巣の入口の大きさ比較に鉛筆を置いてあります
03:43
So this is the colony founded by a queen the previous summer.
59
211000
4000
これは昨夏出来たばかりのコロニーです
03:47
This is a three-year-old colony.
60
215000
2000
これは3年目のコロニーです
03:49
There's the nest entrance, there's a pencil for scale.
61
217000
4000
巣の入口の大きさ比較に鉛筆を置いてあります
03:53
They make a midden, a pile of refuse -- mostly the husks of the seeds that they eat.
62
221000
5000
アリが作るゴミの山は大方が食糧の種の皮です
03:58
This is a five-year-old colony. This is the nest entrance, here's a pencil for scale.
63
226000
5000
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
04:03
This is about as big as they get, about a meter across.
64
231000
3000
巣は大きくても直径1m程度です
04:07
And then this is how colony size and numbers of worker ants changes --
65
235000
5000
このグラフはコロニーの大きさを表す働きアリの数が
04:12
so this is about 10,000 worker ants --
66
240000
3000
コロニーの年数とともにどう変化するかを示します
04:15
changes as a function of colony age, in years.
67
243000
3000
これは働きアリ約1万匹です
04:18
So it starts out with zero ants, just the founding queen,
68
246000
5000
最初は女王アリだけで 働きアリ０匹から始まり
04:23
and it grows to a size of about 10 or 12 thousand ants when the colony is five.
69
251000
4000
5年経つまでに1万～1万2千匹ほどまで増加します
04:27
And it stays that size until the queen dies
70
255000
3000
その後 15～20歳になった女王アリが
04:30
and there's nobody to make more ants, when she's about 15 or 20 years old.
71
258000
5000
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
04:35
And it's when they reach this stable size, in numbers of ants,
72
263000
4000
アリの数がここまで安定すると
04:39
that they start to reproduce.
73
267000
2000
アリは繁殖し始めます
04:41
That is, to send more winged queens and males to that year's mating flight.
74
269000
6000
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
04:47
And I know how colony size changes as a function of colony age
75
275000
5000
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
04:52
because I've dug up colonies of known age and counted all the ants. (Laughter)
76
280000
5000
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
04:59
So that's not the most fun part of this research, although it's interesting.
77
287000
5000
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
05:04
(Laughter)
78
292000
1000
（笑）
05:05
Really the question that I think about with these ants is what I call task allocation.
79
293000
5000
私が知りたいのは このアリの仕事の割当てです
05:10
That's not just how is the colony organized,
80
298000
3000
コロニーの組織のされ方ではなく
05:13
but how does it change what it's doing?
81
301000
2000
いかに動きが変わるのか？
05:15
How is it that the colony manages to adjust
82
303000
4000
状況の変化と共に 各仕事につく働きアリの数を
05:19
the numbers of workers performing each task as conditions change?
83
307000
4000
いかにコロニーは調整しているのか？
05:23
So, things happen to an ant colony.
84
311000
2000
色々なことが考えられます
05:25
When it rains in the summer, it floods in the desert.
85
313000
3000
夏の雨で砂漠が氾濫すれば
05:28
There's a lot of damage to the nest,
86
316000
2000
巣には大きな被害が出て
05:30
and extra ants are needed to clean up that mess.
87
318000
3000
後片付けをするアリが余分に必要となります
05:33
When extra food becomes available --
88
321000
2000
たくさん食糧が調達できる時は
05:35
and this is what everybody knows about picnics --
89
323000
2000
ピクニックでよく見かけるように
05:37
then extra ants are allocated to collect the food.
90
325000
3000
食糧収集にいつも以上のアリが配置されます
05:40
So, with nobody telling anybody what to do, how is it that
91
328000
3000
指揮監督なしで いかにコロニーでは
05:43
the colony manages to adjust the numbers of workers performing each task?
92
331000
4000
各仕事に就くアリの数を調整するのでしょう？
05:47
And that's the process that I call task allocation.
93
335000
3000
これは私が仕事分配と呼んでいる過程です
05:51
And in harvester ants, I divide the tasks
94
339000
2000
巣の外で見かける
05:53
of the ants I see just outside the nest
95
341000
2000
アリの仕事を
05:55
into these four categories: where an ant is foraging,
96
343000
3000
４種に分類しました
05:58
when it's out along the foraging trail, searching for food or bringing food back.
97
346000
5000
外で食糧を調達してくる食糧アリ
06:03
The patrollers -- that's supposed to be a magnifying glass --
98
351000
3000
虫メガネを持っている偵察アリは
06:06
are an interesting group that go out early in the morning
99
354000
2000
食糧アリの活動前に
06:08
before the foragers are active.
100
356000
2000
早朝から動きだす面白い集団です
06:10
They somehow choose the direction that the foragers will go,
101
358000
3000
どういうわけか 偵察アリは食糧アリが行く方向を決め
06:13
and by coming back -- just by making it back --
102
361000
3000
その方向から無事に帰ってくることで
06:16
they tell the foragers that it's safe to go out.
103
364000
3000
外出しても安全だと食糧アリに教えます
06:19
Then the nest maintenance workers work inside the nest,
104
367000
3000
整備アリは巣の中で働きます
06:22
and I wanted to say that the nests look a lot like Bill Lishman's house.
105
370000
5000
巣はビル リシュマンの家にそっくりです
06:27
That is, that there are chambers inside,
106
375000
2000
と言うのも 中に小室があって
06:29
they line the walls of the chambers with moist soil
107
377000
4000
湿った土で小室の壁を覆うと
06:33
and it dries to a kind of an adobe-like surface in it.
108
381000
3000
日干し煉瓦のように乾きます
06:36
It also looks very similar to some of the cave dwellings
109
384000
3000
この地域に見られるホピ族の
06:39
of the Hopi people that are in that area.
110
387000
3000
洞窟住居にも類似しています
06:42
And the nest maintenance workers do that inside the nest,
111
390000
4000
整備アリは巣の中をそのように施し
06:46
and then they come out of the nest carrying bits of dry soil in their mandibles.
112
394000
3000
大あごで乾いた土を地上に運びます
06:49
So you see the nest maintenance workers come out with a bit of sand,
113
397000
3000
砂を持って出てくる整備アリは
06:52
put it down, turn around, and go back in.
114
400000
2000
砂を置き 方向転換して 戻ります
06:54
And finally, the midden workers put some kind of territorial chemical in the garbage.
115
402000
8000
最後に ごみアリは ある縄張り物質をゴミにつけます
07:02
So what you see the midden workers doing is making a pile of refuse.
116
410000
3000
ごみアリはゴミの山を作るんです
07:05
On one day, it'll all be here, and then the next day
117
413000
2000
その日によって違った場所に
07:07
they'll move it over there, and then they'll move it back.
118
415000
2000
ゴミの山を作りだします
07:09
So that's what the midden workers do.
119
417000
4000
それがごみアリの仕事です
07:13
And these four groups are just the ants outside the nest.
120
421000
4000
この4つのグループは巣の外で仕事をするアリで
07:17
So that's only about 25 percent of the colony, and they're the oldest ants.
121
425000
4000
全体のわずか25％で 最年長アリです
07:21
So, an ant starts out somewhere near the queen.
122
429000
3000
どのアリも女王アリの近くから出てきたわけです
07:24
And when we dig up nests we find they're about as deep
123
432000
3000
掘り起こすと 巣はコロニーの幅ほどの深さがあり
07:27
as the colony is wide, so about a meter deep for the big old nests.
124
435000
4000
大きくて古い巣は深さが1mほどあります
07:31
And then there's another long tunnel and a chamber, where we often find the queen,
125
439000
5000
つるはしで岩を８時間叩き割って行くと
07:36
after eight hours of hacking away at the rock with pickaxes.
126
444000
4000
長い通路の奥の小部屋に女王アリを見つけます
07:40
I don't think that chamber has evolved because of me and my backhoe
127
448000
4000
我々がショベルカーやつるはしで掘り起こした為に
07:44
and my crew of students with pickaxes,
128
452000
2000
小室がこの形になったとは思いません
07:46
but instead because when there's flooding,
129
454000
2000
時々起こる洪水のため
07:48
occasionally the colony has to go down deep.
130
456000
3000
コロニーは深さがなくてはいけません
07:51
So there's this whole network of chambers.
131
459000
2000
それで これほどまでの小室があるのです
07:53
The queen's in there somewhere; she just lays eggs.
132
461000
3000
女王アリはどこかで産卵だけしています
07:56
There's the larvae, and they consume most of the food.
133
464000
3000
幼虫は食糧のほとんどを消費します
07:59
And this is true of most ants --
134
467000
2000
ほとんどのアリに共通していることですが
08:01
that the ants you see walking around don't do much eating.
135
469000
2000
外で見かけるアリはあまり食べることをしません
08:03
They bring it back and feed it to the larvae.
136
471000
2000
食糧を調達し幼虫に餌付けします
08:05
When the foragers come in with food, they just drop it into the upper chamber,
137
473000
5000
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
08:10
and other ants come up from below, get the food,
138
478000
3000
下から別のアリがやってきて食糧を受け取り
08:13
bring it back, husk the seeds, and pile them up.
139
481000
3000
運んで種の皮をむき 積み上げます
08:16
There are nest maintenance workers working throughout the nest.
140
484000
3000
整備アリは巣の至る所で働いています
08:19
And curiously, and interestingly, it looks as though at any time
141
487000
5000
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
08:24
about half the ants in the colony are just doing nothing.
142
492000
3000
何もしていないかのように見えるのです
08:27
So, despite what it says in the Bible,
143
495000
2000
聖書には “怠け者よ
08:29
about, you know, "Look to the ant, thou sluggard,"
144
497000
4000
アリのところに行ってみよ” とありますが
08:33
in fact, you could think of those ants as reserves.
145
501000
3000
このようなアリは補欠選手と考えてもいいでしょう
08:36
That is to say, if something happened -- and I've never seen anything like this happen,
146
504000
3000
私の20年の研究では見たことがありませんが
08:39
but I've only been looking for 20 years --
147
507000
2000
いざという時には
08:41
if something happened, they might all come out if they were needed.
148
509000
4000
全てのアリが出てくるかも知れません
08:45
But in fact, mostly they're just hanging around in there.
149
513000
2000
でも 大抵その辺でうろついているだけです
08:47
And I think it's a very interesting question --
150
515000
2000
私が興味を惹かれるのは
08:49
what is there about the way the colony is organized
151
517000
3000
何もしていないアリの予備軍に何か役割を出しうる
08:52
that might give some function to a reserve of ants who are doing nothing?
152
520000
7000
コロニーの組織のされ方とは何なのか？
08:59
And they sort of stand as a buffer in between
153
527000
4000
何もしないアリは巣の奥深くで働くアリと
09:03
the ants working deep inside the nest and the ants working outside.
154
531000
3000
外で働くアリの調停者のような立場にいます
09:06
And if you mark ants that are working outside, and dig up a colony,
155
534000
4000
外で働くアリに印をつけてコロニーを掘ると
09:10
you never see them deep down.
156
538000
2000
絶対に彼らを巣の奥で見かけません
09:12
So what's happening is that the ants work inside the nest when they're younger.
157
540000
5000
と言うのもアリは若い時に巣の中で働くのです
09:17
They somehow get into this reserve.
158
545000
2000
いつの間にか この補欠組に入り
09:19
And then eventually they get recruited to join this exterior workforce.
159
547000
4000
ついには外で働くアリとなります
09:23
And once they belong to the ants that work outside, they never go back down.
160
551000
4000
一度外で働くようになると地中には戻りません
09:28
Now ants -- most ants, including these, don't see very well.
161
556000
3000
大方のアリは目がよく見えません
09:31
They have eyes, they can distinguish between light and dark,
162
559000
3000
明暗を見分けられる程度の目で
09:34
but they mostly work by smell.
163
562000
2000
ほとんどを嗅覚に頼っています
09:36
So just to reinforce that what you might have thought
164
564000
4000
ですから女王アリが指揮していると思われたら
09:40
about ant queens isn't true --
165
568000
2000
それは違います
09:42
you know, even if the queen did have the intelligence
166
570000
3000
女王アリがアリ全体に指令を出せる―
09:45
to send chemical messages through this whole network of chambers
167
573000
4000
化学的なメッセージを送る知能を持っていたとしても
09:49
to tell the ants outside what to do,
168
577000
2000
そんなメッセージで
09:51
there is no way that such messages could make it in time to see
169
579000
4000
適切なタイミングに働きアリの仕事割り当ての
09:55
the shifts in the allocation of workers that we actually see outside the nest.
170
583000
5000
変更を届けられることは絶対にあり得ないので
10:00
So that's one way that we know the queen isn't directing the behavior of the colony.
171
588000
4000
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
10:05
So when I first set out to work on task allocation,
172
593000
3000
仕事分配の研究を始めたとき
10:08
my first question was, "What's the relationship
173
596000
3000
最初の疑問は “別の仕事をするアリ同士の
10:11
between the ants doing different tasks?
174
599000
3000
関係はどうなっているか” でした
10:14
Does it matter to the foragers what the nest maintenance workers are doing?
175
602000
3000
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？
10:17
Does it matter to the midden workers what the patrollers are doing?"
176
605000
3000
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？
10:20
And I was working in the context of a view of ant colonies in which each ant
177
608000
6000
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
10:26
was somehow dedicated to its task from birth
178
614000
3000
自分の位置は知っていても
10:29
and sort of performed independently of the others,
179
617000
3000
他のアリとは独立して作業しているという見方で
10:32
knowing its place on the assembly line.
180
620000
2000
研究をしていました
10:34
And instead I wanted to ask, "How are the different task groups interdependent?"
181
622000
4000
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
10:38
So I did experiments where I changed one thing.
182
626000
2000
条件を一つ変えて実験をしてみました
10:40
So for example, I created more work for the nest maintenance workers
183
628000
4000
例えば 整備アリが活動をし始める朝早くに
10:44
by putting out a pile of toothpicks near the nest entrance,
184
632000
4000
巣の入口近くに楊枝を積み上げて
10:48
early in the morning when the nest maintenance workers are first active.
185
636000
4000
整備アリの仕事を増やしてみました
10:52
This is what it looks like about 20 minutes later.
186
640000
2000
約20分後にはこのようになり
10:54
Here it is about 40 minutes later.
187
642000
2000
約40分後にはこのようになりました
10:56
And the nest maintenance workers just take all the toothpicks
188
644000
2000
整備アリは楊枝を巣の端に運び
10:58
to the outer edge of the nest mound and leave them there.
189
646000
3000
そこに放置するのです
11:01
And what I wanted to know was, "OK,
190
649000
3000
それで次に浮かんだ疑問は
11:04
here's a situation where extra nest maintenance workers were recruited --
191
652000
3000
いつも以上の整備アリが召集された場合
11:07
is this going to have any effect on the workers performing other tasks?"
192
655000
4000
別の仕事をしているアリに影響は出るのか？
11:11
Then we repeated all those experiments with the ants marked.
193
659000
4000
印をつけたアリで再度実験を行いました
11:15
So here's some blue nest maintenance workers.
194
663000
3000
青く印をつけた整備アリです
11:18
And lately we've gotten more sophisticated
195
666000
2000
最近は以前より凝って
11:20
and we have this three-color system.
196
668000
2000
３色使っています
11:22
And we can mark them individually so we know which ant is which.
197
670000
3000
1匹ずつ印をつけるので個体が識別できます
11:25
We started out with model airplane paint
198
673000
2000
最初はプラモデル用のペンを
11:27
and then we found these wonderful little Japanese markers,
199
675000
2000
使いましたが その後 日本製の
11:29
and they work really well.
200
677000
2000
優れたペンを見つけました
11:31
And so just to summarize the result,
201
679000
2000
結果はと言うと
11:33
well it turns out that yes, the different tasks are interdependent.
202
681000
3000
異なる仕事は互いに関係があり
11:36
So, if I change the numbers performing one task,
203
684000
3000
ある仕事をしているアリの数を変えれば
11:39
it changes the numbers performing another.
204
687000
2000
別の仕事をするアリの数も変わります
11:41
So for example, if I make a mess
205
689000
2000
例えば 私が何か散らかして
11:43
that the nest maintenance workers have to clean up,
206
691000
2000
整備アリの仕事量を増やせば
11:45
then I see fewer ants out foraging.
207
693000
2000
食糧アリは見かけなくなりました
11:47
And this was true for all the pair-wise combinations of tasks.
208
695000
3000
これはすべての仕事に共通していました
11:50
And the second result, which was surprising to a lot of people,
209
698000
5000
多くの人を驚かせた2つ目の結果は
11:55
was that ants actually switch tasks.
210
703000
2000
アリが役割を切り替えることです
11:57
The same ant doesn't do the same task over and over its whole life.
211
705000
4000
アリは一生を通じて同じ仕事はしません
12:01
So for example, if I put out extra food, everybody else --
212
709000
3000
例えば 余分な食糧を置いてみると
12:04
the midden workers stop doing midden work and go get the food,
213
712000
2000
ごみアリはごみ収集を止め食糧調達に行き
12:06
they become foragers.
214
714000
2000
食糧アリと化します
12:08
The nest maintenance workers become foragers.
215
716000
2000
整備アリが食糧アリとなり
12:10
The patrollers become foragers.
216
718000
2000
偵察アリが食糧アリになります
12:12
But not every transition is possible. And this shows how it works.
217
720000
4000
全ての役割変換が可能なわけではありません
12:16
Like I just said, if there is more food to collect, the patrollers, the midden workers,
218
724000
4000
先ほどのように 食糧があれば 偵察アリもごみアリも
12:20
the nest maintenance workers will all change to forage.
219
728000
2000
整備アリも食糧アリに替わります
12:22
If there's more patrolling to do --
220
730000
2000
障害を作ることで
12:24
so I created a disturbance, so extra patrollers were needed --
221
732000
4000
通常よりも偵察が必要ならば
12:28
the nest maintenance workers will switch to patrol.
222
736000
2000
整備アリは偵察アリに替わります
12:30
But if more nest maintenance work is needed --
223
738000
3000
しかし 楊枝を積み上げて
12:33
for example, if I put out a bunch of toothpicks --
224
741000
2000
整備の仕事を増やしても
12:35
then nobody will ever switch back to nest maintenance,
225
743000
3000
整備アリに戻るアリはおらず
12:38
they have to get nest maintenance workers from inside the nest.
226
746000
3000
巣の中から整備アリを召集しなくてはいけません
12:41
So foraging acts as a sink, and the ants inside the nest act as a source.
227
749000
6000
巣の中のアリからスタートして 食糧探しがゴールです
12:48
And finally, it looks like each ant is deciding
228
756000
2000
最後に アリが活動するかどうかは
12:50
moment to moment whether to be active or not.
229
758000
3000
その時々で決めているようです
12:53
So, for example, when there's extra nest maintenance work to do,
230
761000
4000
例えば 整備の仕事が増えても
12:57
it's not that the foragers switch over. I know that they don't do that.
231
765000
4000
食糧アリは仕事を切り替えずに
13:01
But the foragers somehow decide not to come out.
232
769000
2000
巣から出てきません
13:03
And here was the most intriguing result: the task allocation.
233
771000
4000
一番興味深い結果だったのは仕事分担です
13:07
This process changes with colony age, and it changes like this.
234
775000
4000
この過程はコロニーの古さと共に変化します
13:11
When I do these experiments with older colonies --
235
779000
3000
5年から10年経過した―
13:14
so ones that are five years or older --
236
782000
2000
古めのコロニーで実験をすると
13:16
they're much more consistent from one time to another
237
784000
3000
一貫性がより強く見られ恒常的です
13:19
and much more homeostatic. The worse things get,
238
787000
2000
状況が悪化するほど
13:21
the more I hassle them, the more they act like undisturbed colonies.
239
789000
3000
せかされるほど 平静を装います
13:24
Whereas the young, small colonies --
240
792000
2000
それに対し 新しくて小さな
13:26
the two-year-old colonies of just 2,000 ants -- are much more variable.
241
794000
4000
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
13:30
And the amazing thing about this is that an ant lives only a year.
242
798000
5000
驚くのはアリの寿命がわずか1年であること
13:35
It could be this year, or this year.
243
803000
2000
いつ生まれても1年です
13:37
So, the ants in the older colony that seem to be more stable
244
805000
4000
古めのコロニーの落ち着いて見えるアリは
13:41
are not any older than the ants in the younger colony.
245
809000
3000
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
13:44
It's not due to the experience of older, wiser ants.
246
812000
3000
年の功ではありません
13:47
Instead, something about the organization
247
815000
2000
その代わりに組織に関わる何かが
13:49
must be changing as the colony gets older.
248
817000
3000
コロニーが古くなるにつれて変わるに違いありません
13:52
And the obvious thing that's changing is its size.
249
820000
3000
明らかに変化しているのはコロニーの大きさです
13:55
So since I've had this result, I've spent a lot of time trying to figure out
250
823000
6000
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
14:01
what kinds of decision rules -- very simple, local, probably olfactory, chemical
251
829000
6000
単純で 局所的で おそらく嗅覚に関わり 化学的で
14:07
rules could an ant could be using, since no ant can assess the global situation --
252
835000
5000
観察可能なアリの決断規則を
14:12
that would have the outcome that I see,
253
840000
3000
突きとめようと時間をかけてきました
14:15
these predictable dynamics, in who does what task.
254
843000
3000
誰がどの仕事をするのか予測できる過程
14:18
And it would change as the colony gets larger.
255
846000
3000
そしてそれはコロニーの老化と共に変化します
14:21
And what I've found out is that ants are using a network of antennal contact.
256
849000
7000
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
14:28
So anybody who's ever looked at ants has seen them touch antennae.
257
856000
3000
アリを観察したことのある方なら知っているでしょう
14:31
They smell with their antennae.
258
859000
2000
アリは触角で匂いをかぎ分けます
14:33
When one ant touches another, it's smelling it,
259
861000
2000
アリがアリを触るのは 匂いを嗅いでいるのです
14:35
and it can tell, for example, whether the other ant is a nest mate
260
863000
4000
同じ巣の仲間かどうか確認できるのです
14:39
because ants cover themselves and each other, through grooming,
261
867000
4000
コロニー独自の匂いがする油の層で
14:43
with a layer of grease, which carries a colony-specific odor.
262
871000
4000
お互いにグルーミングして体を覆います
14:47
And what we're learning is that an ant uses the pattern of its antennal contacts,
263
875000
5000
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
14:52
the rate at which it meets ants of other tasks, in deciding what to do.
264
880000
5000
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
14:57
And so what the message is, is not any message
265
885000
3000
アリからアリへのメッセージではなく
15:00
that they transmit from one ant to another, but the pattern.
266
888000
4000
パターンがあるのです
15:04
The pattern itself is the message.
267
892000
2000
パターン自体がメッセージです
15:06
And I'll tell you a little bit more about that.
268
894000
2000
後からまた説明しますが
15:08
But first you might be wondering:
269
896000
2000
アリはいかに自分の役割が
15:10
how is it that an ant can tell, for example, I'm a forager.
270
898000
5000
わかるのでしょう 例えば自分が食糧アリならば
15:15
I expect to meet another forager every so often.
271
903000
2000
他の食糧アリと頻繁に会うはずです
15:17
But if instead I start to meet a higher number of nest maintenance workers,
272
905000
4000
その代わりに沢山の整備アリと会ったら
15:21
I'm less likely to forage.
273
909000
2000
おそらく食糧探しには行きません
15:23
So it has to know the difference between
274
911000
2000
そうなると食糧アリと整備アリの違いを
15:25
a forager and a nest maintenance worker.
275
913000
2000
見分けなくてはいけないのです
15:27
And we've learned that, in this species --
276
915000
3000
他の種も同じだと思いますが
15:30
and I suspect in others as well --
277
918000
3000
この種のアリの体についている―
15:33
these hydrocarbons, this layer of grease on the outside of ants,
278
921000
4000
油の層の炭化水素は
15:37
is different as ants perform different tasks.
279
925000
3000
仕事により異なることがわかりました
15:40
And we've done experiments that show that
280
928000
2000
実験でわかったのは
15:42
that's because the longer an ant stays outside,
281
930000
2000
アリが外にいる時間が長くなるほど
15:44
the more these simple hydrocarbons on its surface change,
282
932000
4000
体の表面の単純な炭化水素が変わるので
15:48
and so they come to smell different by doing different tasks.
283
936000
3000
仕事によって体の匂いも異なるのです
15:51
And they can use that task-specific odor in cuticular hydrocarbons --
284
939000
4000
仕事ごとに違う匂いを角皮の炭化水素に使えるのです
15:55
they can use that in their brief antennal contacts to somehow
285
943000
4000
短時間の触角の接触の中で 匂いを使って
15:59
keep track of the rate at which they're meeting ants of certain tasks.
286
947000
4000
特定の仕事のアリと会う割合を把握します
16:03
And we've just recently demonstrated this
287
951000
3000
我々は最近 炭化水素の抽出物を
16:06
by putting extract of hydrocarbons on little glass beads,
288
954000
4000
小さなガラス玉につけ 適切な割合で
16:10
and dropping the beads gently down into the nest entrance at the right rate.
289
958000
4000
巣の入口にそっと落とすことで証明してみました
16:14
And it turns out that ants will respond to the right rate of contact
290
962000
4000
そうするとアリは炭化水素つきのガラス玉に
16:18
with a glass bead with hydrocarbon extract on it,
291
966000
3000
本物のアリと接触するように
16:21
as they would to contact with real ants.
292
969000
3000
反応することがわかったのです
16:26
So I want now to show you a bit of film --
293
974000
3000
少し映像をお見せしますが
16:33
and this will start out, first of all, showing you the nest entrance.
294
981000
5000
まず見えるのは巣の入口部分です
16:38
So the idea is that ants are coming in and out of the nest entrance.
295
986000
3000
アリが巣に出たり入ったりしています
16:41
They've gone out to do different tasks, and the rate at which they meet
296
989000
5000
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
16:46
as they come in and out of the nest entrance determines, or influences,
297
994000
4000
別のアリと会う割合が 外に出るかどうかや
16:50
each ant's decision about whether to go out, and which task to perform.
298
998000
4000
どの仕事をするかという判断に影響を与えます
16:54
This is taken through a fiber optics microscope. It's down inside the nest.
299
1002000
4000
光ファイバー顕微鏡を使って巣の中を撮影しました
16:58
In the beginning you see the ants
300
1006000
2000
初めに光ファイバー顕微鏡と
17:00
just kind of engaging with the fiber optics microscope.
301
1008000
2000
接触しているのアリが見えます
17:02
But the idea is that the ants are in there,
302
1010000
4000
巣の中のアリはどれも
17:06
and each ant is experiencing a certain flow of ants past it --
303
1014000
5000
すれ違って行くアリを感知し
17:11
a stream of contacts with other ants.
304
1019000
3000
他のアリと接触しています
17:14
And the pattern of these interactions determines
305
1022000
3000
この関わり合いのパターンで
17:17
whether the ant comes back out, and what it does when it comes back out.
306
1025000
5000
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
17:22
You can also see this in the ants just outside the nest entrance like these.
307
1030000
7000
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
17:29
Each ant, then, as it comes back in, is contacting other ants.
308
1037000
4000
どのアリも巣の中に戻ると他のアリと接触しています
17:33
And the ants that are waiting just inside the nest entrance
309
1041000
3000
巣の入り口のすぐ中で待っていたアリは
17:36
to decide whether to go out on their next trip,
310
1044000
3000
入ってくるアリと接触して
17:39
are contacting the ants coming in.
311
1047000
2000
外に出かけるか決めます
17:41
So, what's interesting about this system is that it's messy.
312
1049000
4000
このシステムの面白い部分は乱雑なところです
17:45
It's variable. It's noisy. And, in particular, in two ways.
313
1053000
5000
特に2つの点において可変的で混沌としています
17:50
The first is that the experience of the ant -- of each ant -- can't be very predictable.
314
1058000
5000
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
17:55
Because the rate at which ants come back depends on
315
1063000
3000
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
17:58
all the little things that happen to an ant as it goes out and does its task outside.
316
1066000
5000
アリに起きている状況次第だからです
18:03
And the second thing is that an ant's ability to assess this pattern
317
1071000
5000
二つ目は高度な計算が出来るアリはいないので
18:08
must be very crude because no ant can do any sophisticated counting.
318
1076000
6000
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
18:15
So, we do a lot of simulation and modeling, and also experimental work,
319
1083000
4000
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
18:19
to try to figure out how those two kinds of noise combine to,
320
1087000
6000
その2種類の情報がコロニーの
18:25
in the aggregate, produce the predictable behavior of ant colonies.
321
1093000
4000
予測出来る行動を生み出すのか探究しています
18:31
Again, I don't want to say that this kind of haphazard pattern of interactions
322
1099000
5000
このような偶然の接触パターンが
18:36
produces a factory that works with the precision and efficiency of clockwork.
323
1104000
7000
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
18:43
In fact, if you watch ants at all, you end up trying to help them
324
1111000
3000
実際アリの観察を始めると 彼らがすべきことを
18:46
because they never seem to be doing anything
325
1114000
2000
彼らがしているようには見えないため
18:48
exactly the way that you think that they ought to be doing it.
326
1116000
3000
結局手助けしてしまうことになります
18:51
So it's not really that out of these haphazard contacts, perfection arises.
327
1119000
7000
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
18:58
But it works pretty well.
328
1126000
2000
でも うまく働いています
19:00
Ants have been around for several hundred million years.
329
1128000
3000
アリは数百万年も生きてきた生き物で
19:03
They cover the earth, except for Antarctica.
330
1131000
3000
南極大陸を除き 至る所で生息しています
19:06
Something that they're doing is clearly successful enough
331
1134000
4000
彼らの偶然的な接触のパターンは
19:10
that this pattern of haphazard contacts, in the aggregate,
332
1138000
3000
全体としてアリを繁栄させるのを可能にする―
19:13
produces something that allows ants to make a lot more ants.
333
1141000
4000
何かを可能にしているのです
19:17
And one of the things that we're studying is how natural selection
334
1145000
3000
我々は自然選択がいかにして
19:20
might be acting now to shape this use of interaction patterns --
335
1148000
7000
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
19:27
this network of interaction patterns --
336
1155000
2000
コロニーの食糧探しの効率化を上げるのに
19:29
to perhaps increase the foraging efficiency of ant colonies.
337
1157000
5000
影響しているかを研究しています
19:34
So the one thing, though, that I want you to remember about this
338
1162000
3000
覚えておいていただきたいのは
19:37
is that these patterns of interactions
339
1165000
3000
この相互作用パターンは
19:40
are something that you'd expect to be closely connected to colony size.
340
1168000
5000
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
19:45
The simplest idea is that when an ant is in a small colony --
341
1173000
5000
一番単純な考えは アリがコロニーの大きさに関係なく
19:50
and an ant in a large colony can use the same rule,
342
1178000
4000
同じルールを使うという考えです
19:54
like "I expect to meet another forager every three seconds."
343
1182000
4000
例えば “3秒毎に食糧アリと会う” と予測しても
19:58
But in a small colony, it's likely to meet fewer foragers,
344
1186000
3000
小さいコロニーで それほど食糧アリに会いません
20:01
just because there are fewer other foragers there to meet.
345
1189000
4000
食糧アリの数が少ないからなのです
20:05
So this is the kind of rule that, as the colony develops and gets older and larger,
346
1193000
6000
この種のルールがあれば コロニーが成長するにつれて
20:11
will produce different behavior in an old colony and a small young one.
347
1199000
5000
異なる行動が生み出されます
20:16
Thank you.
348
1204000
2000
ありがとうございました
20:18
(Applause)
349
1206000
2000
（拍手）
ABOUT THE SPEAKER
Deborah Gordon - EcologistBy 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?
Deborah Gordon | Speaker | TED.com