The Lost Penile Spines
消失的阴茎刺
Scientists believe men once had small spines on their genitalia such as those found in chimpanzees, cats and mice.
科学家们相信，男性的阴茎上曾经有小刺，这种小刺与黑猩猩，猫和老鼠身上所发现的一样。
Analysis of the genomes of humans, chimpanzees and macaques indicates that a DNA sequence thought to play a role in the production of these spines have been deleted in humans, but has been preserved in other primates.
在对人、黑猩猩和赫猴的基因组进行分析时可以发现，一个被认为对这种小刺的生成起作用的DNA序列在人类身上已经被除去，但在其他的灵长类动物身上却保留了下来。
It suggests another genetic deletion may have led to the expansion of specific regions of the human brain. The study is in the journal Nature.
这就表明，可能是另一个基因的缺失导致了人类大脑某特定区域的扩张。这项研究发表在了《自然》杂志上。
The researchers at Stanford, Georgia and Pennsylvania State universities in the US wanted to trace evolutionary changes in human DNA.
美国佐、治亚州斯坦福大学和宾夕法尼亚州立大学的研究人员们想要探索出人体的DNA在进化中的演变轨迹。
They compared the human genome with those of the chimpanzee and macaque, and came up with 510 stretches of DNA that have been conserved in our primate relatives but deleted in humans. Nearly all these DNA regions appear to play a regulatory role in the function of nearby genes.
他们把人的基因组同黑猩猩及赫猴的进行比对，发现有510个基因片段被保存在我们的近亲灵长类动物身上，但在人类身上却已缺失，而几乎所有的这些DNA区域都在功能上对其附近的基因起着调节作用。
The researchers then focused on two deletions, linking one to penile spines and another to the growth of specific areas of the brain. They then tested the effects of the deleted sequences in human skin and neural tissue, and found further evidence to support their claims.
之后，研究人员就把目光集中到两个缺失的基因片段上，其中一个与阴茎刺有联系，另一个与大脑某特定区域的发育相关。然后他们又对该缺失的基因序列能对人体皮肤和神经系统组织产生怎样的影响进行了检测，找到了支撑他们主张的更深层的证据。
"We're trying to find the molecular basis of being human," said Professor David Kingsley of Stanford University, one of the authors of the study. "That's a really ambitious goal; but we live at this unique time where we have the complete genome sequence of ourselves and our closest relatives, so you can systematically go through and find all the ways that we differ from other organisms."
"我们正在试图找到能够成为人的分子基础"，斯坦福大学教授、也是本研究的合著者之一的戴维·金斯利教授讲道"这可真是一个很远大的目标，但是，既们生活在这么一个特殊的时期，我们既有了自身完整的基因序列，又有了我们的近亲的完整基因组序列，那么我们就可以系统地梳理并找出我们和其他生物的不同之处。"
Penile spines are barb-like structures found in many mammals. Their role remains under debate, and they may play different roles in different species.
在许多哺乳动物身上，我们发现阴茎刺呈倒钩状结构。不过对于它们存在的意义，目前仍有争议。或许，对于不同的物种，它们所起的作用也不一样。
They may increase stimulation for the male during mating. They might also play a part in inducing female ovulation in a small number of species, but there is evidence that they can cause damage to the female too.
在交配过程中，这种小刺或许能增强雄性的快感。同样，对于一少部分物种而言，它们可能还能起到促使雌性排卵的作用。但是有证据表明，它们也会给雌性物种带来伤害。
Then there is the suggestion that they might have evolved to remove "mating plugs" -material that some male species deposit in the female genital tract to block other males' attempts to fertilise the same female.
于是就有了这样一种说法，这种小刺可能在进化中可以去除"交配插头"——一种雄性在雌性生殖道内留下的物质，这种物质可以阻止其他雄性试图使该雌性受孕。
"It's been proposed these structures can help remove the copulatory" plugs left by other males; so in some mammals with multi-male mating systems, there's quite a little arms race going on for fertilisation," said Professor Kingsley.
金斯利教授说有人称，这些结构可以帮助去除其他雄性所遗留下来的交配插头，所以一些在多雄交配系统中的哺乳动物，为了受精，的确是存在小小的军备竞赛的"。
The researchers believe the loss of these spines in humans may be related to changes in human courtship. The loss of spines, they say, would result in less sensitivity，and longer copulation, and may be associated with stronger pair-bonding in humans and greater paternal care for human offspring.
研究人员认为，人类身上这种小刺的消失，可能是和人求爱的过程、方式等发生的变化有关。他们说，失去了这种小刺，其结果就是会降低敏感度，但延长了相应的交配时间;而且这可能和人类较强的一夫一妻观念和父亲对后代的关爱有关。