• CBS pre-Ep1 "Troyzan vs. Tarzan" ad
• CBS "Meet Greg" pre-game video
• Full CBS "Meet the Cast" video

• Official CBS Survivor: One World bio page

Collection of images from the preview and other circa-Ep1 One World footage:

Vidcap gallery: Click on thumbnails to expand; use arrow keys to navigate between enlarged pics.

From MSN.com's pre-game interview with Jeff Probst:

"Greg says: In the operating room I am king. One on one with someone, I'm scared to death. I'm only doing it for the adventure and the romance. Watch out. I can talk your ears off. I am hoping to play a pseudo-father, kind fatherly role to help my tribe.

Jeff says: Dr. Greg Smith, otherwise known as Tarzan, is one of the smartest guys we've ever had on the show. I told him right before the game started, 'Your biggest obstacle is your own ego and feeling you need to tell everybody how smart you are and how good at everything you are.' And if he does that, they'll get rid of him. My prediction: He's gone early."

From his CBS bio page:

"Personal Claim to Fame: Board Certification in General Surgery and Plastic Surgery, receiving a 1st place award for research in reconstructive surgery, playing for 'Doug Silvers & the Starliters' as an organ/pianist, 4th place as Campion Missouri State Wrestler Light Heavyweight and a marriage for 30 years to a true "soul mate."
Inspiration in Life: Tarzan, who is empathic toward nature; kind, brave, noble, "manly," and Scaramouche (the Raphael Sabatinni version) – a statesman, romantic, adventurer, swordsman and empathic toward the needs to women.
Hobbies: Art, music, adventure, entomology and primatology.
Pet Peeves: Inequity and deceit.
3 Words to Describe You: Creative, childlike, (but not childish) and honorable.
Survivor Contestant You Are Most Like: Coach Ben Wade – he seems to be a romantic, adventurer, poetic and creative.
Reason for Being on Survivor: The adventure, the challenge; to lose weight.
Why You Think You'll 'Survive' Survivor: I'm of the jungle and part of nature.
Why You Think You Will Be the Sole Survivor: Other than the misfortunes of contretemps, I hope to outwit, outplay, outlast."

Summary of evidence for Greg Smith being on Survivor: One World.

- castaway208 (12/6/11), having spoiled much of the rest of the cast already, started by giving clues about an older, long-haired, bearded contestant with a hippie-ish vibe.
- Following the airing of the post-South Pacific preview of One World, castaway208 (12/18/11) confirmed: yes, that's him in the preview.

Who is Greg Smith?

Until his pre-game bio and interviews come out, your guess is as good as ours.