Svaret är Människan, men sen kan ni ju läsa följande konversation saxad ur boken Pyramids av Terry Pratchett.
'Yes, but,' said Teppic crouching down and brushing a clear space on the damp sand, 'is there internal consistency within the metaphor? Let's say for example that the average life expectancy is seventy years, OK?'
'OK,' said the Sphinx, in the uncertain tones of someone who has let the salesman in and is now regretfully contemplating a future in which they are are undoubtedly going to buy life insurance.
'Right. Good. So noon would be age 35, am I right? Now considering that most children can toddle at a year or so, the four legs reference is really unsuitable, wouldn't you agree? I mean, most of the morning is spent on two legs. According to your analogy-' he paused and did a few calculations with a convenient thighbone- 'only about twenty minutes immediately after 00.00 hours, half an hour tops, is spent on four legs. Am I right? Be fair.'
'Well-' said the Sphinx.
'By the same token you wouldn't be using a stick by six p.m. because you'd be only, er, 52.' said Teppic, scribbling furiously. 'In fact you wouldn't really be looking at any kind of walking aid until at least half past nine, I think. That's on the assumption that the entire lifespan takes place over one day which is, I believe I have already pointed out, ridiculous. I'm sorry, it's basically OK, but it doesn't work.'
-Carniel