As Grok crested the rise upon which his tribe's caves sat, he began to ponder the effects of the sun on his mud soaked skin. The twigs and moss on his back interwove eachother, criss crossing through the gradually hardening dirt to form a kind of carapace on his fur. He was contemplating his recent inventions, the spike, the circle, and the act of humourously awakening from a dream sequence, with an air of one who is skirting around a breakthrough so amazing, so earth shattering, so god damned crazy, that the very nature of their existence will shift like a tide when it happens.
He also needed to wee.
'Aarrghhrrhnanannaaggrh' he sang soothingly to himself as he urinated over a small prehistoric mammal of indeterminate identity.
His thoughts tripped over themselves.
His lovelife, his weapon, the hunt, respect, the wheel, and the hard surface of mud on his back.
He felt like they should somehow combine... Grok knew that if the outcome was right, he would not only be the talk of the tribe, but he would no longer have to smack women over the head to woo them.
The wheel... The hard, virtually impenetrable mud casing... The hide piercing spike... Grok rocked back and forth, and waited for the inspiration to hit him.