So in the comics, Mentor and Kronos put Arthur Douglas's spirit into a new, more powerful body in order to help defeat Thanos, but (speaking as someone who hasn't read the comics but is interested in the back story of the character) is there any evidence to suggest what species Drax the Destroyer's body is? Is it just a modified human body? Or is it alien?
Drax the Destroyer started his career (in the Marvel Earth-616 canon) as a Human spirit tied to cosmically-enhanced soil. He would later be killed and reanimated with a body that appears human with strange sigils on his shoulders and/or back. Drax in the Marvel Cinematic Universe is not the same character that appears in the canon Marvel Comics Universe. In the Guardians of the Galaxy franchise, Drax is a member of a primitive and as yet unnamed species who lack the ability to easily comprehend metaphorical statements.
In the Marvel Cinematic Universe, Earth-199999
Drax is a humanoid of an undetermined species who has through the use of technology or perhaps ritual scarification, scored an image of various skulls and other death-oriented iconography on his body. A closeup of said tattoos reveals the ornate and macabre nature of the images. Given that his people are considered technological primitives, scarification is the more likely source.
The origins, rationals and explanations for said imagery has only been hinted at and is believed to have been due to the loss of his family.
Because of said loss, he is said to have taken to the spaceways to find and get his revenge on Ronan, the Accuser. Despite his formidable fighting prowess, he was no match for the technologically-enhanced Accuser.
If and whether he has superhuman abilities is not made clear in the Marvel Cinematic Universe, however Drax is a superb fighter, quite durable, utterly fearless, and incredibly ferocious in battle.
In the canon Marvel Comic Universe, Earth-616
Drax the Destroyer was an ordinary human, Arthur Douglas, who was killed by the Mad Titan, Thanos. Sensing an imbalance in the universe, the abstract entity Kronos, brought back to life and empowered Douglas with what he believed would be sufficient power to battle and destroy Thanos.
- In Drax's first incarnation he had superhuman strength, the ability to project bursts of energy and was capable of space flight. He was for all intents and purposes, physically invulnerable. However, his mind was vulnerable to powerful psychic attacks.
Drax's first appearance was in Iron Man #55 (February 1973), created by writer Mike Friedrich and writer/artist Jim Starlin.
- Drax would fight Thanos on several occasions and would later team up with the original Captain Marvel, the enigmatic being called Adam Warlock and would one day become a member of Warlock's Infinity Watch.
Note the skull iconongraphy which shows up on all the Destroyer designs from this period. The skull motif is worked into the new prosthetics as well. Drax on the left was the calm and cerebral version, the one on the right, was powerful but childlike in intelligence.
Drax's mind would be later destroyed when he confronted his daughter, the telepathic metahuman known as Moondragon after she has enslaved a planet using her powers. He would lie inert for some time before his resurrection by Kronos. He is returned to life, stronger than ever, in the hopes he would counter the renewed threat of Thanos returning to life as well. Drax is eventually restored to his fully powered and intelligent form and after some further adventures retires to the Microverse.
When we find Drax in the mainstream Marvel Universe again, he is onboard a prison transport and he and four other prisoners are enroute to the Galactic Maximum Security Prison called the Kyln. Drax is killed by four of the other prisoners (The Blood Brothers, Paibok, the Power Skrull and Lunatik). In Drax's defense, his mind was scrambled and he was not fighting at his best.
After a night of regeneration, he is reborn (Drax the Destroyer Vol. 1, Issue 3; 2007) into a smaller, leaner form with strange red tattoos on his shoulders that sweep across his back and chest. No explanation had been given for the tattoos. Curiously, depending on the artist, they change their appearance unexpectedly and without explanation.
- After his rebirth, Drax has lost his all of his energy manipulation abilities and flight, but retained his durability and some degree of superhuman strength (though nowhere near his previous Hulk-level strength). He also discovered a preference for his trademark knives in combat.
While Arthur Douglas was originally a normal human, the current comic version of Drax is made of... dirt + a whole lot of magic.
Kronos and Mentor then fashioned a humanoid body from the Earth's soil, granted it superhuman powers, and cast Douglas' spirit inside it. Thus they created the being who would become known as Drax the Destroyer.
It can be noted that the body created by Kronos and Mentor was green and looked vaguely Skrull-like.
He was later killed and resurrected. When restored, his appearance had changed with no explanation. In particular, he now sports his inexplicable trademark tattoos
His origins and/or species is different depending on which Marvel continuity you reference:
Comics Version: One of a kind creation
Within the comics 616 continuity, Drax is one-of-a-kind. Mentor and Kronos put the soul of dying human Arthur Douglas into a newly-created body, intended as a weapon against Thanos. He was later killed and afterwards regenerated into a new body that appeared similar, yet slightly different from the first. The panels below are from Captain Marvel #32 (February 1974), which is a retelling of his origin:
Original (non-human) body
Second (non-human) body
Movie Version: Unknown species
The MCU version of Drax is apparently a member of a species that has no concept of metaphors, and therefore take everything literally. This version of Drax is based on the second appearance of Drax in the comics. His red tattoos, appearing similar to tiger stripes in the comics, is here presented as tattoos or ritual scarification which tells the story of his life. During the lineup scene, it was shown that the Nova Corps has no knowledge of his species or homeworld.
It's very possible that we will learn more about Drax in the upcoming sequel.