很多人说，人类的嗅觉正在慢慢退化。
但一项新研究告诉我们：嗅觉不是简单变弱，而是一直在被饮食、生存方式重新塑造。
狩猎采集部落的人，能凭气味分辨草木、追踪野兽，他们的基因，也保留着更完整的嗅觉感知能力。我们的鼻子，藏着一部漫长的人类演化史。
Scientists are learning more about the genetics of humans’ smelling skills
HUMANS, AS AN EVOLUTIONARY GROUP, are often said to be losing their sense of smell. “But our sense of smell is not simply declining,” says Lian Deng of the School of Life Sciences at China’s Fudan University. “It is still being reshaped by lifestyle, diet and even culture.” That’s the upshot of a recent study aimed at revealing how the genetics of human olfaction has changed over the past few millennia.
The study grew from the fieldwork of Hoh Boon-Peng, a geneticist at the IMU University in Malaysia, who saw how important smell still is in the daily life of the region’s hunter-gatherers. They follow their noses to distinguish among herbs, identify ripe fruit and figure out where animals have traveled—they can even tell what kind of animal has passed by based on the smell of its urine—and their language has a strikingly rich vocabulary for odors, Hoh says. Such observations led Deng to ask whether smell’s enduring importance might have left detectable traces in the evolution of smell-recognition genes. In the study, published in Cell Reports, Deng, Hoh and their colleagues analyzed genomes from 50 Indigenous people from the Malay Peninsula and compared them with other populations around the world. The sample included the hunter-gatherers and two other Indigenous groups that focus on farming and agriculture.
The results suggest that the Malay Peninsula hunter-gatherers have preserved a more complete set of smell-receptor genes than the other groups studied. In most populations around the world, many of these genes have accumulated mutations over time that have left about 60 percent of them nonfunctional. But the hunter-gatherers showed significantly fewer mutations in their olfactory-receptor genes. The intact gene variants they carry are linked to sensing earthy, floral and fruity smells—cues essential to food and other vital resources.
The genetic differences among the populations did not pertain only to smell. In one of the farming groups, the researchers identified a distinct version of a receptor gene called OR12D3. Previous studies have linked this gene to insulin secretion, suggesting it may reflect adaptation to the higher-carbohydrate diet that came with agriculture.
Even among modern humans, sense of smell varies widely from person to person, and much of that variation is thought to come from differences in odor-receptor genes, says Duke University molecular geneticist Hiroaki Matsunami, who was not involved in the work. To him, the study provides evidence that humans’ recent evolutionary history might have helped shape these genes.
Deng says hunter-gatherer populations, long underrepresented in genomic research, have allowed the survival of genetic signatures tied to ancient history and have also led to new adaptations. “Such living populations can be invaluable for understanding the deep history of human genetic diversity,” she adds.
嗅觉的演化变迁
科学家正在进一步揭开人类嗅觉能力背后的基因奥秘
作为演化分支，人类常被认为嗅觉正在不断退化。复旦大学生命科学学院的邓莲表示：“但人类嗅觉并非单纯地衰退，它还在被生活方式、饮食乃至文化持续重塑。”这是一项最新研究得出的核心结论，该研究旨在揭示过去数千年间，人类嗅觉的基因发生了怎样的变化。
这项研究起源于马来西亚国际医药大学遗传学家何文彬的实地考察。他观察到，在当地狩猎采集族群的日常生活里，嗅觉依旧至关重要。这些族群依靠鼻子分辨草药、辨识成熟果实，追踪动物行踪；甚至仅凭尿液气味，就能判断出是哪种动物途经此地。何文彬提到，他们的语言中，描述气味的词汇格外丰富。这些观察启发邓莲思考：嗅觉的重要地位，是否会在气味识别基因的演化中留下可检测的痕迹。
研究成果发表于《细胞报告》。邓莲、何文彬及其团队分析了马来半岛50位原住民的基因组，并与全球其他人群做对比。样本包含狩猎采集族群，以及另外两个以农耕为主的原住民群体。
研究结果显示，马来半岛的狩猎采集族群，保留了一套比其他受试群体更完整的嗅觉受体基因。在全球大多数人群中，这类基因历经岁月积累突变，大约六成已经失去功能。而狩猎采集族群的嗅觉受体基因，突变数量显著更少。他们所携带的完整基因变体，与感知泥土、花草、果香有关——这些气味线索，是寻找食物与生存资源的关键。
不同人群之间的基因差异，并不只体现在嗅觉上。在其中一个农耕族群中，研究者发现了受体基因OR12D3的独特变体。此前研究表明，该基因和胰岛素分泌相关，这或许反映出人类为适应农耕带来的高碳水饮食，产生了演化适应。
杜克大学分子遗传学家松浪博明并未参与本次研究，他介绍：即便是现代人类，嗅觉的个体差异也十分巨大，很大一部分差异来源于嗅觉受体基因的不同。在他看来，这项研究证明，人类近代演化史，塑造了这类基因。
邓莲说，基因组研究中长期缺少狩猎采集族群的数据，而这些人群保留着和远古历史相关的遗传印记，同时也演化出新的适应性特征。她补充道：“这类现存族群，对探索人类基因多样性的悠远历史有着不可估量的价值。”
