We know both from the original series and Star Trek Beyond that the vulcan heart is located where the human liver is. It seems an odd and inconvenient position deprived of the protection the rib cage provides for humans.

So I'm wondering if there is any evolutionary logic behind this anatomy explained somewhere.

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    There's no logic to "evolution." It would be better to ask why the Creator placed the heart in the position He did for Vulcans, but such a question would probably offend too many people. – Ham Sandwich Mar 13 '17 at 2:41
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    @T-1000'sSon Of course evolution has a logic, it's called natural selection where traits that permit a differential survival and reproduction of individuals persist. Some traits are neutral, but I'm betting an exposed heart is not. And Valorum actually gave a good answer. – Ram Mar 13 '17 at 2:44
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    I think you will find that the human liver is largely also protected by the rib cage. img.webmd.com/dtmcms/live/webmd/consumer_assets/site_images/… – Timbo Mar 13 '17 at 4:51
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    BTW, it seems that the chief function ("en.wikipedia.org/wiki/Rib_cage#Function") of the human rib cage is to support the core of the body (shape and muscle attachments) and the respiratory system: breathing would be much less efficient if it were less rigid. Protection from blows is an added plus. – can-ned_food Mar 13 '17 at 5:03
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    ....of course, you need your liver to survive anyways. Losing it would probably take longer than if it had been your heart, but it's likely to have been fatal regardless. – Clockwork-Muse Mar 13 '17 at 7:19

This is addressed in the Star Fleet Medical Reference Manual, considered a canon source of information about the physiology of aliens.


The Vulcan heart beats at the astounding rate of 242 bests per minute. The average blood pressure is 90 systolic, and 40 diastolic. This phenomenon is explained in part by the extremely dilated blood vessels of Vulcans. Large diameter blood vessels are an additional aid in cooling the body, allowing for greater cooling surface.

The Vulcan heart is located where one would expect to find the Terran liver, leaving room for the somewhat larger Vulcan lung assembly. In consequence, the cartilage that normally protects the Terran heart extends an extra 3.5 cm downward in a Vulcan in order to protect this vital organ.

enter image description here

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    And where is the liver located? – Dunebro Mar 13 '17 at 10:35
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    @Dunebro - See edit. – Valorum Mar 13 '17 at 10:39

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