So, if I remember correctly, Sark said this dark planet is the size of Jupiter, correct? If so, and if I did my math right, the amount of human(oid) bodies needed to mash together a Jupiter-sized planet would be 215,554,490,000,000,000,000,000 (or 2.1555449e23 or 215.554 sextillion). So there's that.
(This is based on the assumption that Jupiter's volume is 1,431,281,810,739,360 km3 and the volume of a human body is 0.06640 m3.)