Wait until Spike gets older. If he's male, he will have a bulge and femoral pores along his rear legs. I don't have a pic I can post, go ahead and google "bearded dragon femoral pores" to get a good idea of what they look like. A female will have no femoral pores at all.
"Your absence has gone through me like thread through a needle. Everything I do is stitched with its color."