Observe the close resemblances between placental mammals and their marsupial counterparts here:

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However, there is a caveat here. Both placentals and marsupials are mammals, distantly related, but related nonetheless. Hence the pre-existence of such structures as skeletons, teeth, etc, etc must have exerted a significant effect upon the common convergence of functions and structures.

Therefore, I expect at least SOME ETIs to superficially resemble humans:

1. I expect SOME kind of skeleton, either internal (like vertebrates) or external (like arthropods). A flexible animal like an octopus would have a very difficult time moving swiftly on land in an aerobic environment.

2. Two eyes, two ears, two arms, at least two legs, etc because these are essential. Eyes and ears are obvious. I expect that for and hind limbs would be differentiated into arms and legs. Arms are for manipulation. Without the ability to manipulate their environment, intelligence would be useless. Legs are for locomotion. Without the ability to move around, they would be pretty well helpless.

3. I expect them to live on land in oxygen-rich air and not in water. Water is unsuitable for important purposes, such as building fires, and fire is the very central factor in human technology. Water is the most abundant compound in the Universe, and its use as a hydrogen donor will almost certainly occur wherever photosynthetic life emerges. This necessarily releases oxygen.

4. I expect them to breathe their oxygen-rich air. As a consequence, I anticipate that their respiratory passages will become adapted for vocalization as a secondary function. Hence, I anticipate that they will communicate by talking, although in a different manner from us. Given the necessity of ears, and the availability of respiratory passages for adaptation into vocal apparatus, communication by vocalization strikes me as the easiest way to go. Language of some sort is a must.

5. The temporary nature of sound will force them to invent written communications via symbols. These will be the foundation of higher civilizations as they have proven to be on Earth.