事实：
1）一篇发表在《自然》（Nature）杂志上的关于酵母菌适用雪堆搏弈模型的研究报告见诸该杂志的网络版，发表在该杂志的通信（Letters）栏目中，全文于2009年4月8日登出。
2）该研究由麻省理工学院（MIT）的学者完成，作为院方公众形象管理的一部分，其新闻办公室在2009年4月6日，由Anne Trafton执笔就发出了报道，该报道发表在“科学界”（Insciences.org）的网页上：http://insciences.org/article.php?article_id=4121，该报道有该研究的详细介绍，针对原文作者进行了采访，附合一般科学报道原则。该文也送至了另外多个网上登出，比如这里：http://pda.physorg.com/cooperativebehavior-yeast-evolutionarytheory_news158245420.html
3）在“科学界”报道之后，其它网站也有跟进，比如TS-SI（专门针对同性恋进行科学研究与宣传机构）在次日有一篇未署名的报道，这一篇报道中对雪堆博弈有详细介绍。http://www.ts-si.org/evolution/4507-meshing-cooperative-behaviors-with-evolutionary-theory.html
4）方舟子于2009年4月12日跟进，完成《好人与骗子的博弈》，该文提供的信息除囚徒困境外，全部可以在上面的文章中找到，用不着查看《自然》原文。而关于囚徒困境部分，方舟子全文抄自Drexel大学Roger A. McCain教授的个人网页对搏弈论的介绍：http://william-king.www.drexel.edu/top/eco/game/dilemma.html。
5）Anne Traflon在原文中说，“The researchers observed that cooperating yeast have preferential access to approximately 1 percent of the sucrose they produce. That benefit outweighs the cost of helping others, allowing them to successfully compete against cheaters.”方舟子于是乎扩展成为“麻省理工学院的研究人员最近发现，好人生产的单糖并不是100％拿出来共享的，而是自己会截留一小部分，虽然私藏的这部分很少（只占约1％），却让好人在利用单糖方面比骗子有了一点优势，在一定条件下这点优势超过了制造单糖的成本，就会让当好人在总体上比当骗子更有优势。”这是属于典型的臆想式的抄袭，在Anne Traflon并不准确描述该研究的基础上，方舟子为了避免直接抄袭而加以想象扩展，跟他在《蟑螂的民主决策》一文中犯下的毛病是一样的，不查看原始研究文章，仅仅根据新闻报道开始“创作”（实为编译），别人错一小步，方舟子拐一大弯，跟原始研究就错得远了。在原始研究文章中，该论文说明在特定条件下，“合作”类型的菌株对转化酶转化的单糖估计只有1%利用效率：“The fraction of invertase-created glucose that is captured can be estimated by dividing the rate of glucose uptake of cells growing in 0.003% glucose by the measured rate of invertase activity, yielding an estimated glucose capture efficiency of only~1%”。其实，读者不象该研究的学者那么醉心于用“搏弈论”去硬套酵母菌，很容易想到这是产生转化酶的菌株的一种特点，几乎可以称为缺陷，之所以不称为缺陷，因为此类菌株可以比不能产生此种酶的菌株更能适应环境。此类菌株如果在细胞内转化蔗糖，那么其利用效率就大大提高了，当然，那时，研究人员就不会找它来做实验了，单糖在水中自由扩散而为其它菌株或者生物利用，跟“合作”菌是否有“合作”意愿与精神毫不相干。
6）方舟子一文在一个有缺陷的研究的基础上，加倍扩展了其谬误，对搏弈论甚为无知，根据他对Anne Traflon报道（及其它报道）中不准确描述的扩充，可以判定方舟子实际上是编译了不超过三篇英文非专业性的网络文章而炮制了一篇垃圾“科普”，最为搞笑的是，他最后似懂非懂地跑来煸情，“举世皆好人时当骗子，举世皆骗子时当好人，这样最有可能获得成功”，这一句话真是方舟子既打假又假打的充分写照！在现实世界中，他就是在骗子面前充好人，而在好人面前欺诈行骗毫无内疚，这下实践可联系上“理论”了。
7）方舟子曾与人言：“如果是翻译、编译国外的文章，而不注明，当成自己的原创文章发表，那是剽窃行为”，看来方舟子是知道写作的一般道德规范的，可惜，这个道德规范是衡量别人的。对不起，咱们也要用这个规范衡量方舟子自己。
附一：《自然》杂志原文及补充材料
附二：Anne Traflon的科技新闻报道
The Games Microbes Play - Game theory study in yeast shows how cooperative behavior meshes with evolutionary theory
Published on 6 April 2009, 10:19 Last Update: 2 week(s) ago by Insciences
Categories: Bioengineering | Physics | Yeasts |
One of the perplexing questions raised by evolutionary theory is how cooperative behavior, which benefits other members of a species at a cost to the individual, came to exist.
Cooperative behavior has puzzled biologists because if only the fittest survive, genes for a behavior that benefits everybody in a population should not last and cooperative behavior should die out, says Jeff Gore, a Pappalardo postdoctoral fellow in MIT’s Department of Physics.
Gore is part of a team of MIT researchers that has used game theory to understand one solution yeast use to get around this problem. The team’s findings, published in the April 6 online edition of Nature, indicate that if an individual can benefit even slightly by cooperating, it can survive even when surrounded by individuals that don’t cooperate.
Physics postdoctoral fellow Jeff Gore, left, and physics professor Alexander van Oudenaarden are harvesting yeast cells for experiments exploring the evolution of cooperation.
In short, the study offers a concrete example of how cooperative behaviors can be compatible with evolutionary theory.
Yeast may seem unlikely subjects for a study of cooperative behavior, but in fact they are perfectly suited to such studies, says Gore. Unlike humans, yeast have no emotions or thoughts that interfere with rational decision-making; their actions are solely driven by their genetic response to the environment.
"You can apply game theory to biological interactions and in some ways it’s more broadly applicable than it is in humans," says Gore, the paper’s lead author.
Game theory, traditionally employed by economists and military strategists, uses mathematics to predict individuals’ behavior in certain situations.
Cooperators and cheaters
Working with MIT physics professor Alexander van Oudenaarden, also an author of the paper, Gore developed an experimental setup involving yeast sucrose metabolism. Sucrose is not yeast’s preferred food source, but they will metabolize it if no glucose is available. To do so, they must secrete an enzyme called invertase, which breaks sucrose into smaller sugars that the yeast can absorb.
Much of that sugar diffuses away and is freely available to other yeast cells in the environment. In this scenario, yeast that secrete invertase are known as cooperators, while those that don’t secrete invertase and instead consume the simple sugars produced by others are called cheaters.
If all of these simple sugars diffused away, with no preferential access to the yeast that produced it, then it would always be better to cheat, and the cooperators would die out.
The researchers observed that cooperating yeast have preferential access to approximately 1 percent of the sucrose they produce. That benefit outweighs the cost of helping others, allowing them to successfully compete against cheaters.
In addition, no matter the initial starting numbers of yeast in a given population, the microbes always come into an equilibrium state, with both cooperators and cheaters present. "It doesn’t matter where you start. You always end up with equilibrium," says Gore.
This suggests that the yeast are playing what game theorists call a snowdrift game. The name of the game comes from a situation in which two drivers are trapped in cars behind a snowdrift. Each one can choose to get out and clear a path or stay put. If one driver does not shovel, the other must.
The best option is to "cheat" by staying in the car while the other driver shovels. However, the worst-case scenario occurs if both drivers cheat and no one gets home. Therefore, the best strategy is always the opposite of your opponent’s strategy.
The same rules apply to the cheating and cooperating yeast: Like the driver who grudgingly gets out and shovels so that both she and her fellow motorist — snug inside his car — may continue on their journeys, the yeast who cooperate do so because there is a slight benefit for themselves. However, when most of the yeast are cooperating, it becomes advantageous for some individuals to cheat, and vice versa, which allows co-existence between cheaters and cooperators to arise.
Studies have shown that in the wild, yeast carry different numbers of copies of the invertase gene. This genetic diversity in the wild may be similar to the long-term coexistence of cooperators and cheaters observed in the laboratory, says Gore.
Hyun Youk, an MIT graduate student in physics, is also an author of the paper. This research was funded by the National Institutes of Health and the National Science Foundation.
By Anne Trafton, News Office
Contact: Elizabeth Thomson, Senior Science & Engineering Editor , Phone: 617-258-5402 | thomson@mit.edu
Source: MIT, Massachusetts Institute of Technology
附三：TS-SI报道中对雪堆搏弈的说明
The Snowdrift Game
Consider a situation in which two drivers are trapped in cars behind a snowdrift. Each one can choose to get out and clear a path or stay put. If one driver does not shovel, the other must.
The best option is to "cheat" by staying in the car while the other driver shovels. However, the worst-case scenario occurs if both drivers cheat and no one gets home. In The Snowdrift Game the best strategy is always the opposite of your opponent’s strategy.
This is an example of the interplay between cheating and cooperation. One driver grudgingly gets out and shovels so that both she and the other motorist — inside his warm car — may continue their journey. The driver who cooperates does so because there is a slight benefit to herself, which allows co-existence between a cheater and a cooperator.
In this game, individuals gain direct benefits from cooperative acts, which may indicate why cooperation is favored by natural selection.
For comparison, consider The Prisoner’s Dilemma. Two prisoners being questioned; each one has a choice: betray the other and assign guilt or defend the other’s innocence. As in the Snowdrift game, the best option is to betray your opponent while he defends you. There is a lesser reward for both of you to defend each other. As in the Snowdrift Game, if both betray the other, there is no payoff for either person.
The difference between the two games lies in the greater risk posed by the Prisoner’s Dilemma when you cooperate while your opponent defects. There is always a benefit to shoveling snow, even when the opponent sits and does nothing. Defending an opponent who betrays you results in the worst possible outcome for you: no payoff at all.
Game theorists often view these two games as variants of Chicken (also known as Hawk-Dove), an influential conflict model for two players.
The basic principle is that while each player prefers not to yield to the other, the outcome where neither player yields is the worst possible for both players. The game has also been used to describe the mutual assured destruction of nuclear warfare.
附四：McCain博士个人网页中对搏弈论囚徒困境介绍中方舟子抄袭部分原文
This remarkable innovation did not come out in a research paper, but in a classroom. As S. J. Hagenmayer wrote in the Philadelphia Inquirer ("Albert W. Tucker, 89, Famed Mathematician," Thursday, Feb. 2, 1995, p.. B7) " In 1950, while addressing an audience of psychologists at Stanford University, where he was a visiting professor, Mr. Tucker created the Prisoners’ Dilemma to illustrate the difficulty of analyzing" certain kinds of games. "Mr. Tucker’s simple explanation has since given rise to a vast body of literature in subjects as diverse as philosophy, ethics, biology, sociology, political science, economics, and, of course, game theory."
The Game
Tucker began with a little story, like this: two burglars, Bob and Al, are captured near the scene of a burglary and are given the "third degree" separately by the police. Each has to choose whether or not to confess and implicate the other. If neither man confesses, then both will serve one year on a charge of carrying a concealed weapon. If each confesses and implicates the other, both will go to prison for 10 years. However, if one burglar confesses and implicates the other, and the other burglar does not confess, the one who has collaborated with the police will go free, while the other burglar will go to prison for 20 years on the maximum charge.
The strategies in this case are: confess or don’t confess. The payoffs (penalties, actually) are the sentences served. We can express all this compactly in a "payoff table" of a kind that has become pretty standard in game theory. Here is the payoff table for the Prisoners’ Dilemma game:
Table 3-1 （略，请参见原文，方舟子没有用此表）
The table is read like this: Each prisoner chooses one of the two strategies. In effect, Al chooses a column and Bob chooses a row. The two numbers in each cell tell the outcomes for the two prisoners when the corresponding pair of strategies is chosen. The number to the left of the comma tells the payoff to the person who chooses the rows (Bob) while the number to the right of the column tells the payoff to the person who chooses the columns (Al). Thus (reading down the first column) if they both confess, each gets 10 years, but if Al confesses and Bob does not, Bob gets 20 and Al goes free.
So: how to solve this game? What strategies are "rational" if both men want to minimize the time they spend in jail? Al might reason as follows: "Two things can happen: Bob can confess or Bob can keep quiet. Suppose Bob confesses. Then I get 20 years if I don’t confess, 10 years if I do, so in that case it’s best to confess. On the other hand, if Bob doesn’t confess, and I don’t either, I get a year; but in that case, if I confess I can go free. Either way, it’s best if I confess. Therefore, I’ll confess."
But Bob can and presumably will reason in the same way — so that they both confess and go to prison for 10 years each. Yet, if they had acted "irrationally," and kept quiet, they each could have gotten off with one year each.
附五：方舟子《好人与骗子的搏弈》
1950年，美国数学家阿尔伯特·塔克在斯坦福大学给心理学家做报告时，讲了一个故事。警察在盗窃现场附近抓到了两名疑犯阿尔和鲍勃，把他们分开审讯，并分别向他们开了条件：如果两人都不招供（疑犯彼此“合作”），警方没有他们盗窃的证据，将以携带武器这一较轻的罪名各判处一年监禁。如果两人都招供并牵连对方（疑犯彼此“背叛”），两人都将各判处10年监禁。如果有一人招供并牵连对方，而对方不招供，此人将被免于起诉，而对方将被判处最高刑期20年。
阿尔会想：“鲍勃要么招供要么不招。如果鲍勃招了，而我不招，那么我将被判20年，我招了则被判10年。如果鲍勃不招，我也不招，那么我将被判1年，但是如果我招了，我将被免于起诉。所以不管鲍勃招不招，我招供都是最好的选择。”鲍勃也这么想。最终两人因为都“理性”地选择招供而被判了10年。但是如果他们都“非理性”地选择不招，则只会被判1年。
理性的选择却不能带来最佳的结果，这个“囚徒困境”后来成了博弈论最著名的问题。博弈论还有一个类似的问题也是关于合作与背叛（或欺骗）的关系，但是条件有些不同。有两个人驾车回家，遇到暴风雪，被雪堆分别堵在了街道的两头。司机要么出来铲雪清除路障，要么待在车中。如果两个司机分别从两头铲雪（“合作”），就能都开回家并分担劳动付出。如果只有一个司机铲雪，另一个司机待在车中等对方铲完雪，他也能回家，而且还避免了劳动付出（“欺骗”）。当然，如果两人都待在车中，没人铲雪，那就谁也回不了家了。在这种情况下应该怎么选择呢？最佳的策略是做出与对方相反的选择：如果对方当“好人”铲雪，我就当“骗子”坐等其成；如果对方不铲雪，我就当“好人”自己来铲雪，这样虽然被人占了便宜，总比坐以待毙的好。
博弈论在第二次世界大战结束后不久后出现，本来是为了解决政治学和经济学问题的。上个世纪70年代，它开始被用来解决自达尔文以来就困扰着生物学家的一个生物进化难题：本质上是自私的生物个体为什么会进化出合作行为？它是自然选择作用下不加思索的本能行为，因此就连毫无思考能力的单细胞生物，也会面临着合作还是欺诈的两难，比如酵母菌。
酵母菌通常利用单糖（葡萄糖和果糖）做为营养。如果环境中没有这些单糖，酵母菌也能利用其他糖，例如蔗糖（比单糖复杂的二糖）。但是酵母菌要先把蔗糖消化成单糖，为此需要分泌转化酶来催化这个消化过程。这个消化过程发生在细胞外（更确切地说，发生在细胞膜和细胞壁之间），产生的单糖扩散开去，其他酵母菌也能利用。有的酵母菌的基因发生突变，生产转化酶的基因失去了作用，自己不能分泌转化酶，但是它们能窃取其他酵母菌制造的单糖，又可以节省进行消化的成本。它们成了“骗子”，而那些耗费能量把蔗糖变成单糖的酵母菌成了“好人”（合作者）。
对群体来说，大家当好人彼此合作，全都生产单糖并分享，这样最有优势。但是对个体来说，当骗子最有优势。休斯顿大学的研究人员曾经做过一个实验，结果表明，一个酵母菌群体中好人的密度越大，当骗子的优势就越明显。他们认为这像是“囚徒困境”。在这样的群体中，好人和骗子分享全部的资源，而好人要承担生产成本，因此好人总是竞争不过骗子，一旦出现骗子，它们的后代数量会越来越多，好人的数量会越来越少，等到骗子们统一了天下，末日也就快到了，好人遗留下来的单糖被耗尽后，群体就会灭绝。一个处于“囚徒困境”的群体是很不稳定的。
实际的情形可能比这复杂。麻省理工学院的研究人员最近发现，好人生产的单糖并不是100％拿出来共享的，而是自己会截留一小部分，虽然私藏的这部分很少（只占约1％），却让好人在利用单糖方面比骗子有了一点优势，在一定条件下这点优势超过了制造单糖的成本，就会让当好人在总体上比当骗子更有优势。好人也会有机会。
实验的结果的确如此。在好人的数量比较少、单糖的量也比较少时，能否有效地利用单糖就显得比较重要，好人对单糖的利用率高了1％，其优势较为明显，好人的数量会逐渐增多。等到好人的数量达到一定程度，好人制造单糖花费成本的劣势体现出来了，骗子的优势反而更为明显，骗子的数量就开始逐渐增多了。最终，好人和骗子的比例会达到平衡。实验表明，不管一开始酵母菌群体中的好人和骗子的比例是多少，演变的结果，最后的比例都是一样的。
因此，这更像是“雪堆博弈”，特立独行是最佳策略：举世皆好人时当骗子，举世皆骗子时当好人，这样最有可能获得成功。
2008.4.12
（《中国青年报》2009.4.15）
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