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儿童节的作文-研讨会流程
Puzzles of Evolution
A SINGLE mutation may have cleared the way for rapid brain evolution. Other primates have
strong jaw muscles that exert a force across the whole skull, constraining its growth. But
around 2 million years ago a mutation weakened this grip in the human line. A brain growth
spurt began soon after (Nature, vol 428, p 415).
What
drove
this
spurt
is
another
matter.
The
environment
probably
presented
mental
challenges.
Social developments would have played a part, too. To test the relative importance of these
pressures, David Geary at the University of Missouri in Columbia compared the skull size of
various hominins against environmental conditions each lived in, such as the estimated
variation
in
annual
temperatures,
and
against
proxies
for
social
pressure,
such
as
group
size.
Both were associated with bigger brains, but the difficulties of navigating a larger social
network had the greatest impact (Human Nature, vol 20, p 67).
A big brain is incredibly hungry, so early humans needed to change their diet to support it.
The transition to eating meat would have helped. So would the addition of seafood about 2
million years ago, providing omega-3 fatty acids for brain building (Proceedings of the
National Academy of Sciences, vol 107, p 10002). Cooking might have helped too, by easing
digestion. This would have allowed ancestral humans to evolve smaller guts and devote the
spare resources to brain building.
Big brains come at a price, however, including the dangers of giving birth. By the time the
benefits no longer outweighed the costs, we had a 1.3 kilogram lump of jelly smart enough
to question its own existence.
OUR
ancestors
have
achieved
some
epic
migrations.
Homo
erectus made
the
first
great
trek
out
of Africa and into east Asia 1.8 million years ago. Around a million years later, the
predecessors of Neanderthals turned up in Europe. And 125, 000 years ago, Homo sapiens made
an
early
foray
into
the
Middle
East.
None
of
these
populations
lasted.
But
some
65,
000
years
ago, one group of modern humans left Africa and conquered the world - an extraordinary
achievement for any species, let alone a puny, furless ape. What possessed them to spread
so far and wide?
It
may
have
begun
with
a
big
squeeze.
All
humans
belong
to
one
of
four
mitochondrial
lineages
(L0, L1, L2 and L3) corresponding to four ancestral mothers, but only L3 is found outside
Africa.
Quentin
Atkinson
at
the
University
of
Auckland,
New
Zealand,
and
colleagues
have
found
that this lineage experienced a population explosion in the 10, 000 years leading up to the
exodus (Proceedings of the Royal Society B, vol 276, p 367). So overcrowding in the Horn of
Africa may have pushed the group to cross the Red Sea and move along the southern coast of
Asia.
That still leaves the question of why numbers increased. Atkinson notes that for 100, 000
years the African climate had oscillated between drought and floods before becoming stable
around 70, 000 years ago. Perhaps the environmental instability had forced early humans to
become more inventive, with adaptations that helped population expansion once conditions
improved.
Paul
Mellars
at
the
University
of
Cambridge
has
argued
that
the
explosion
in
numbers
was
driven
by a major increase in the complexity of technological, economic, social and cognitive
1
behaviour (Proceedings of the National Academy of Sciences, vol 103, p 9381). The ability
to control fire came much earlier, as, probably, did language. But the period does see a
blossoming of innovation such as the manufacture of complex tools, efficient exploitation
of
food
sources,
artistic
expression
and
symbolic
ornamentation.
These
cultural
advances
would
have been crucial, says Mark Pagel at the University of Reading, UK.
we can change the world when we get there.
ever
onward,
he
notes,
as
populations
quickly
reached
carrying
capacity
and
individuals
moved
into new territory to avoid competition.
Museum:
the
peopling
of
Australia
may
have
come
about
when
seafarers
travelling
between
islands
were blown further afield. Genetic mutations could also have made us more adventurous. For
example, the so-called novelty-seeking gene, DRD4-7R, is more common in populations that
migrated fastest and furthest from Africa (American Journal of Physical Anthropology, vol
145, p 382).
Stringer.
人类进化十大谜（六
-
七）
也许是某次基因变异为大脑 的快速进化铺平了道路。其他灵长类的颚肌发达，所施加的力量覆盖整个头骨，从而限
制了头骨的生长< br>
。但在
200
万年前，人类这一分支的某个基因突变削弱了这股力量。不久， 大脑陡然开始快速增长
（《自然》第
428
卷第
415
页）
。
促使大脑快速生长的动力却是另一件事。环境很可能形成了对智力的挑战
。社会发展 也起了一部分作用。为了测
试这些压力的相对重要性，来自哥伦比亚密苏里大学的大卫
•
吉利（
David Geary
）对众多古人类的头骨大小与其居住
的环境条件，诸
如年度温差的估值，和社会压力的代数值，
如族群规模，进行了对比
。尽管这两个因素都与大脑
生长有关，但影响最大的是在较大的社会关系网中生存的难度。
大脑袋需要大量的营养，因此早期人类需要改变他们的饮食结构来供养大脑。转而食
肉有所帮助。同样，约
200
万年前开始摄入海鲜食品也为脑部发育提供了欧米伽-3
脂肪酸（《国家科学院院志》第
207
卷第
10002
页） 。烹饪
也有一份贡献，它减轻了消化压力，
使古人类进化出更小的内脏，把省出来的资源用于大脑成长。
A Bright Light Shining Upon Us
The incident was so extreme, it almost defies description. In the wee hours of the morning of 19 March,
astronomers detected from more than halfway across the universe a burst of gamma rays brighter than a
2
hundred-billion suns--and aimed squarely at Earth. Now, after 6 months of analysis, an international team of
astronomers has discovered why the event was so extraordinary.
From brief glimpses throughout the past decade, astronomers have pieced together a standard theory of gamma
ray bursts. When massive stars exhaust their nuclear fuel and can no longer resist the relentless, crushing force of
gravity, they collapse violently. As a star much more massive than the sun contracts to the size of an asteroid--or
even smaller if it becomes a black hole--it creates unimaginable densities, temperatures, and energy. A great deal
of that energy rebounds outward in a jet of particles traveling at nearly the speed of light. When that jet meets
surrounding gas or dust, it generates gamma rays.
New details are revising that picture. A team of 93 scientists report tomorrow in Nature that the
from March --originating in a galaxy about 7.5 billion light- years away in the direction of the constellation
Bootes--shows a feature that has never been seen before. After analyzing data from NASA's Swift spacecraft,
which was designed to move very quickly in the direction of gamma radiation, and other data from both satellite and
ground- based telescopes and detectors, the team says the super bright beam was surrounded by a less energetic,
slower jet about 20 times wider. This could mean, the team suggests, that a bright, narrow beam accompanies all
gamma ray bursts but can't be spotted unless it is aimed directly at Earth.
Events such as the naked-eye burst
past decade, says astrophysicist Joshua Bloom of the University of California, Berkeley. Moreover, this incident
could constitute the first of a remarkable series of glimpses into the most distant parts of the universe, he says. The
burst was so bright, Bloom explains, that it could be observed with relatively small telescopes --and even with the
naked eye. If astronomers get lucky again, they might spy similar bursts from even farther away, perhaps among
the very earliest stars.
/cgi/content/full/2008/910/2
射向地球的一束强光
这是一个如此极端的事件，简直无法形容。
3< br>月
19
日凌晨时分，
天文学家们发现了伽马射线的爆发现象，
射线来自 宇宙半空之外，
比一千亿个太阳还要明亮，
径直地射向地球。
目前，
一个由天 文学家构成的跨国研究小组经过
6
个月的分析之后，发现了这次伽马射线爆发事件为何如此异乎 寻常。
在过去的整整十年中，天文学家们综合了所瞥见的爆发现 象，创建了有关伽马射线爆发的标准理论。当耗尽核燃
料的时候，
大型恒星再也抵挡不住核心引 力造成的残酷的粉碎性重压，
它们发生剧烈塌缩。
一颗比太阳大许多的恒星
塌缩成一颗 小行星大小的星体，如果成为黑洞的话，塌缩后会比小行星更小，因而产生了无法想象的高密度、高温和
3
高能，
其中大量的能量以粒子喷流的形式向外弹回，
以接近光速的速度穿 行于宇宙空间。
当这种喷流遇到周围的气体
或尘埃的时候，伽马射线就产生了。
然而，新发现的详情正在使上述画面有所改动。由
93
名 科学家组成的研究小组在明天出版的《自然》（
Nature
）
杂志上报道：
3
月份，
“
肉眼可见
”
的伽马射线爆发起源于
75
亿光年以外的一个星系中，该星系处于牧夫座的方向上；
这次伽马射线爆发呈现出以前从未见过的特点。 美国国家航空航天管理局
“
雨燕
”
号太空船的设计目的就是为了神速地
对准伽马射线射来的方向。对
“
雨燕
”
号太空船的数据资料，以及对其他太 空和地面望远镜与探测器的数据资料进行分
析之后，研究小组称：这个超级明亮的光束周围是能量较低的 、速度较慢的喷流，其宽度是约光束的
20
倍。研究小
组提出：这有可能意味着，明亮 的细光束伴随着所有的伽马射线，但是其方向若不是直指地球，是不会被发现的。
加州大学伯克利分校的天体物理学家乔舒亚
·
布卢姆指出，在理论学家们利用过去十年 的资料所拼凑起来的那幅简
单画面中，肉眼可见的爆发事件是不存在的。他说：况且，在对最遥远的宇宙 天区进行的一系列引人注目的观测中，
该事件可以算得上是首屈一指的。布卢姆解释说，这次爆发极为明 亮，利用相对小型的望远镜就可以观察到，甚至用
肉眼都可以观察到。
如果再次拥有好运气的话 ，
天文学家们会发现来自更远处的类似爆发，
这种爆发可能会来自一颗
最早的恒星。< br>
True Romance: Love At Long Last
PETER: I was at a skating rink one night when I was 16, in 1958, and I saw this young lady. I waited for you to take
a break and get a Coke before I made
my move. I grabbed you by the hand and said, “My name’s Thomas Peter
Headen.” And you said, “My name’s Jacqueline LeFever.” I looked in those big green eyes, and it was a done deal.
So we dated. Then, in 1959, your father got transferred to Japan. I decid
ed, Well, I’ll go get her. I joined the Marine
Corps, and I said, “I want to go to Japan.” The Marine Corps said, “You’ll go to Japan when we tell you you can go
to Japan.” So I went to a base in California.
JACQUE: I dated a Marine while I was in Japan, and I ended up getting married
—
I guess just because I thought
that’s what I was supposed to do. We came back to the States in 1962, but I didn’t know what happened to you.
4