Note that there are organisms that include &quot;wheels&quot; (Or rather, rotary motion in general).<p>It&#x27;s &quot;just&quot; that the only organisms on Earth that do so are microorganisms. Look at flagella.<p>But there&#x27;s nothing inherent about rotary motion that is impossible for organics to do. It&#x27;s &quot;just&quot; that there is no clear evolutionary path from something that relies on linear actuation to something that relies on rotary actuation.<p>(Also, note that there <i>are</i> pumps that are continuous that don&#x27;t rely on rotary motion. Among other things, you can have two+ sacs, each with an inlet and outlet valve that can contract and expand. One expands while the other contracts, and vice versa. There&#x27;s still some variation while the changeover happens - but this can be avoided if you have &gt;2 sacs. Alternatively, there are peristaltic pumps that work continuously that can be implemented with only linear actuators. (As a bonus, this means that you don&#x27;t need a centralized pump. You can integrate it into the blood vessels themselves.)<p>The bigger limitation tends to be respiratory, actually. Earth has only ~21% oxygen currently. You bump that up (causing all sorts of other problems), you can have faster and&#x2F;or larger critters. Alternatively, you have more efficient lungs (Note that human-style lungs are relatively inefficient. Ideally you want air to flow in one direction through the lungs instead of alternating... Birds do that, IIRC.) and&#x2F;or more efficient oxygen &#x2F; CO2 transport in the blood. Red blood cells are not exactly efficient. (There was an Analog article at one point about diamond spheres for artificial red blood cells. A related article, <a href="https:&#x2F;&#x2F;www.foresight.org&#x2F;Nanomedicine&#x2F;Respirocytes3.html" rel="nofollow">https:&#x2F;&#x2F;www.foresight.org&#x2F;Nanomedicine&#x2F;Respirocytes3.html</a>, says the following &quot;In the absence of respiration or atmospheric oxygen, a fully-O2-charged augmentation dosage consisting of 9.54 x 10^14 respirocytes could provide tissue oxygen delivery and carbon dioxide removal for 12 minutes at peak exertion and 3.8 hours at rest even during cardiostasis&quot; &quot;A 1-liter augmentation dose increases blood O2 storage capacity 18,000%&quot;)