Conjoined twinning is a rare birth defect estimated to occur in about 1 in 50,000 to 100,000 births. The mechanism of conjoined twinning is not proven. Different forms of conjoined twinning are observed with the thoracopagus form being the most common. The rate of conjoined twinning is similar across all major populations. A dramatic malformation of this type would be an extraordinary occurrence leading people to reflect on the spiritual or supernatural nature of such an event. Therefore, it is not surprising that artifacts that seem to depict different forms of conjoined twins are seen across diverse cultures. In this article, we present a survey of these cultural artifacts including anatomic classification based on external anatomy and an exploration of the cultural and spiritual contexts associated with the artifacts. A key finding is that the most common form of conjoined twinning in the artifacts is parapagus (both dicephalus and diprosopus) in contrast to thoracopagus, the most common form in epidemiologic studies. Potential reasons for this difference are discussed. Evidence is presented to support the speculation that these objects represent artistic impressions of actual conjoined twinning events.

中文翻译：

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连体双胞胎的跨文化表征

连体双胞胎是一种罕见的出生缺陷，估计每 50,000 至 100,000 名新生儿中就有 1 人发生。连体孪晶的机制尚未得到证实。观察到不同形式的连体孪晶，其中最常见的是胸廓形式。所有主要人群的连体孪生率相似。这种类型的戏剧性畸形将是一个非同寻常的事件，导致人们反思此类事件的精神或超自然本质。因此，在不同文化中看到似乎描绘不同形式连体双胞胎的文物也就不足为奇了。在本文中，我们对这些文物进行了调查，包括基于外部解剖结构的解剖分类以及对与文物相关的文化和精神背景的探索。一个重要的发现是，与流行病学研究中最常见的胸腹肌形成对比，人工制品中最常见的连体孪生形式是旁翻骨（双头骨和双头骨）。讨论了这种差异的潜在原因。提供的证据支持这些对象代表实际连体孪生事件的艺术印象的推测。