“种”的“通胀”
万岁，林耐
保育学家和北极熊需要留意经济学中的教训
“世上最严肃、最有用的科学，就是经济学”，这是卡尔·林耐的观点，本周
，是这位瑞典博物学家诞生300周年纪念日。人们熟悉他，在于他设计的系统被用
来划分所有生物。
林耐试图揭示他所发现的自然界的神圣秩序，使之可能造福人类。
18世纪的欧洲，大探险和海外贸易带来了许许多多新的生物，特别是一些植
物，被视为潜在的农作物和经济作物。在那时，人们还无法理解各种生物之间的
关系。对它们的描述和分类都是混乱而自说自话的。林耐设计了一个组织系统来
安排整个生物界，“种”是最基本的单位，其上是目和纲。
他的系统被证明既牢靠且灵活，它历经进化论的诞生，并且兼容了迄今为止
发现的所有“种”，比如细菌，林耐从未曾怀疑过它的存在。
但是正如凯恩斯所说的，“摧毁一个社会最好的办法，就是摧毁它的货币”
林耐的系统正在被过于热情的分类学家所侵蚀，他们试图帮助保育事业。
前进，增加
对新地区的详加考察，“种”的数目自然会增加。例如猴子、类人猿、狐猴
的“种”数一直在增加，直到60年代中期，才趋于平稳，但是80年代中期之后，
又再度增加。如今灵长类动物“种”数已两倍于当初的数目。
但是，这并非丛林中的未知“种”被发现，而是很多已确立的亚种被重新划
分为“种”一级单位。
也许“再分类”不一定准确，“重新标签”可能更合适，分类学家并不总是
一开头就正确。当然，起初看起来是一个“种”，之后也可能被分开
………(翻译不出)
之所以发生“种”通胀，在于种的灭绝容易把握，容易制订法规。亚种通常
不能传达足够的政治影响力。亚种地位升级同时增加了珍稀种数（通过种群的片
断化），并且使小块栖地的生物多样性得到提升，而获得要求保护的权利。
就眼前来说，这种策略通过强化灭绝的危险，使情况有利于保育学家。但从长
期来看，正如每个经济学家所知，通胀导致货币贬值。稀有并非完全取决于种的
个体数量，它也取决于该种是如何的与众不同。
如果只有两种大象，亚洲的和非洲的，失去一个意味着很多。如果听从一些分
类学家的意见，将非洲种群再分化，那么，稀有的感觉就会变化。
麻烦的是，如何定义一个种比想象中的要复杂很多。DNA的改变可以导致种的
演化。依靠DNA来划分自然界也许是个好办法。但是，这也取决于你观察哪一段
DNA。举例来说，现代研究表明，北极熊只是灰熊偶然变白，对于依赖濒危动物保
护法的它们来说，这可不是什么好消息。
………（第二、三个例子不翻了，太拗口）
………（最后一段翻译不出，尤其是最后一句）
………………………………我是分割线…………………………………………
Species inflation
Hail Linnaeus
May 17th 2007
From The Economist print edition
Conservationists—and polar bears—should heed the lessons of economics
MEPL
“NO SCIENCE in the world is more elevated, more necessary and more useful than economics.” That was the view of Carl Linnaeus, a Swedish naturalist, born three centuries ago this week, who is better remembered for devising the system used to this day to classify living organisms.
Linnaeus sought to reveal what he saw as the divine order of the natural world so that it might be exploited for human benefit. He lived at a time when exploration and trade were bringing new specimens to the attention of European scientists. Those specimens, particularly the plants, were scrutinised as potential crops. At the turn of the 17th century there was no sense of how creatures were related to each other; descriptions and classifications were unsystematic. Linnaeus gave life to an organising hierarchy with kingdoms at the top and species at the bottom.
The system he created has proved both robust and flexible. It survived the rise of evolution. It also survived the discovery of whole categories of organism, such as bacteria, that the Swede never suspected existed. But, rather as John Maynard Keynes observed that “there is no subtler, no surer means of overturning the existing basis of society than to debauch the currency,” so Linnaeus's system is being subtly debauched by over-eager taxonomists, trying to help conservation.
Go forth and multiply
As new areas are explored, the number of species naturally increases (see article). For example, the number of species of monkey, ape and lemur gradually increased until the mid-1960s, when it levelled off. In the mid-1980s, however, it started rising again. Today there are twice as many primate species as there were then. That is not because a new wave of primatologists has emerged, pith-helmeted, from the jungle with hitherto unknown specimens. It is because a lot of established subspecies have been reclassified as species.
Perhaps “reclassified” is not quite the right word. “Rebranded” might be closer. Taxonomists do not always get it right first time, of course, and what looked like one species may rightly later be seen as two. But a suspiciously large number of the new species have turned up in the limited group of big, showy animals known somewhat disparagingly as “charismatic megafauna”—in other words the species that the public, as opposed to the experts, care about.
One reason for this taxonomic inflation is that the idea of a species becoming extinct is easy to grasp, and thus easy to make laws about. Subspecies just do not carry as much political clout. The other is that upgrading subspecies into species simultaneously increases the number of rare species (by fragmenting populations) and augments the biodiversity of a piece of habitat and thus its claim for protection.
In the short term, this strategy helps conservationists by intensifying the perceived threat of extinction. In the long term, as every economist knows, inflation brings devaluation. Rarity is not merely determined by the number of individuals in a species, it is also about how unusual that species is. If there are only two species of elephant, African and Indian, losing one matters a lot. Subdivide the African population, as some taxonomists propose, and perceptions of scarcity may shift.
The trouble is that the idea of what defines a species is a lot more slippery than you might think. Since it is changes in DNA that cause species to evolve apart, looking at DNA should be a good way to divide the natural world. However, it depends which bit of DNA you look at. The standard technique says, for example, that polar bears are just brown bears that happen to be white. This is not good news for those relying on the Endangered Species Act. For a certain sort of Colorado rodent (with, alas, a nose for prime riverfront real estate) the question of whether it is “Preble's meadow jumping mouse” or a boring old meadow jumping mouse may be a matter of life or death: local property developers are on the death side. The Bahamas switched overnight from protecting their raccoons to setting up programmes to eradicate them when a look at the genetic evidence showed the animals were common Northern raccoons, not a separate species.
The 21st-century answer to this 18th-century riddle is that a species is what a taxonomist says it is. Evolution often fails to produce the clear divisions that human thought in general, and the law in particular, prefers to work with. It therefore behoves taxonomists to be honest. If they debase their currency, it will ultimately become valueless. Linnaeus the economist would have known that instinctively. |
发表于 2007-5-26 14:06:03
发表于 2007-5-27 22:51:27