Theory:Doctor Who television discontinuity and plot holes/The Hungry Earth


 * The central concept of this episode — that the miners have achieved a record by drilling to 21 km, thus threatening the Silurian habitat — is inconsistent with both Inferno and Journey's End. The Inferno Project achieved a depth of at least 20 miles, and the Osterhagen Project placed their nuclear devices beneath the crust of the Earth, which varies between 20 and 70 km in thickness. Humans should therefore have aggravated the Silurians long before this episode. The Osterhagen Project should have been particularly incendiary to Human/Silurian relations, according to the underlying logic of this episode.
 * The Silurians don't live underneath every square inch of the surface. Presumable the Inferno and Osterhagen projects just happened to not be anywhere near any Silurian encampments (and likewise for the Daleks' later attempt to drill all the way down to the Earth's core to remove it so they could take the planet for a joyride), while this one was directly over a major city.
 * Of course that still doesn't explain how 21km could be a record. The Osterhagen project may have deliberately chosen the thinnest parts of the crust (which is actually well under 5km in some spots, especially on the ocean floor--the real-life Project Mohole, the inspiration for Inferno, planned to drill off-shore for exactly this reason). But Inferno was intending to drill all the way to the core, and got as far as 20mi (32km).
 * Maybe Inferno was a well-kept secret. After all, most scientific projects aren't guarded by UNIT.
 * And of course, Torchwood have dug right to the core, and exposed the Racnoss
 * Linking in with the above point both inferno and the osterhagen project were (presumably) secret. So the going by this logic the drilling in this episode will be the deepest official drilling of the earths crust.
 * I don't see how it is inconsistent with the Osterhagen Key, the Inferno Project or the Dalek attempt to hijack the earth's core. These may have plunged the crust nowhere near Silurian settlements. Or perhaps the Silurians are aware of them and choose not to mention them. Or(to use a tired-old device to explain discontinuities) these different events occur in differing timestreams or alternate universes.According to the Doctor, travel to other universes was freely possibly before the fall of Gallifrey.
 * Could the season five crack be responsible for the apparent inconsistency? It has been repeatedly shown throughout this season that key events from the Doctors past never happened as those involved were never born. Could it be that brains behind Osterhagen and Inferno were caught up in the crack? In which case this site in Wales is the deepest hole drilled as the other never happened.


 * Why would a female Silurian have breasts when reptiles don't give their children milk?
 * They aren't reptiles if they are homo reptilia....
 * Under the cladistic system, mammals are just a kind of reptile, so some reptiles do give their children milk.
 * A number of features have been invented multiple times on separate lines. Eyes evolved more times than we can count. Bats developed flight separately from birds. Warm-bloodedness evolved on at least two reptile lines (the one that led to mammals, and the one that led to birds). Bipedalism evolved multiple times. Obviously, in the Whoniverse, intelligence and vocal cords also evolved at least twice on separate lines. So, why couldn't lactation have evolved on another reptile line?


 * Why are they called "Homo reptilia" in the first place? Homo is a genus within the Primate order--in other words, apes. And the Doctor can't just be speaking figuratively--he gives "Homo reptilia" as a more accurate name than the inaccurate "Silurian" or "Eocene". Really, if 300 million years is anywhere close to accurate, attaching them to a 2-million-year-old ape genus is a lot farther off than Silurian, which is at least a period in the same era that they came from, if not the right one.