How do homo sapiens express themselves artistically?

How can paleontologists tell that a set of hominid bones belongs to a separate species from homo sapiens? How do they factor out variability within homo sapiens?

• Humans show a great deal of variability in shape and size. How do we know that the fossils we find that are humanoid are not just weird/unusual/archaic humans?

• Answer:

  As says, it's conceptually and technically difficult.  And in many cases we probably can't tell.  It wasn't until genetic analysis that we learned that some bones that we had assumed were Neandertal, were actually a different species (Denisovians) that we had never even suspected because the bones didn't distinguish them. And we know from other genetic analysis that there was at least one other species that we still haven't distinguished (or maybe we haven't found the bones).   Setting aside the conceptual problem of species, let's think about the technical side.  How, in principle, would we approach the problem? Let's say we have a bone, or bones, that we think may not be H. sapiens.  Maybe it's Neandertal.  There are, broadly speaking, two parts to the approach. First, what's out of normal range? Second, are there clusters? We do have large numbers of H. sapiens bones to look at, so we can pick a character -- let's say, cranial capacity -- and ask what's normal.  We'll get a normal distribution curve (or something more complicated, but let's assume normal distribution).  And we can say that 99.9% of H. sapiens have a cranial capacity between, and I'm making this up, 1000-1500 cm^3.  So if our hypothetical skull has a capacity of 1600 cm^3, we would probably raise our eyebrows.  It's well outside of normal range.  But does that prove it's not sapiens? By no means, because there are still individuals -- some abnormal (hydrocephalic?), some normal (0.1% of 7 billion means there would be millions of people in that range today) -- who would fall into that category. So the next point is clustering.  We found cranial capacity in 0.1% range.  What if we also find bone thickness in the 0.1% range? And also the diameter of the mental foramen was in the 0.1% range? And also the ear bone shapes were in the 0.1% range?  And so on.  Every new characteristic that's outside of normal sapiens range adds new weight to the different species concept. It's harder than that, because you would want to be sure that you're not just looking at the same thing ten times.  If the height is in the 0.1% range and the weight is in the 0.1% range, you don't really have two different characteristics. So you have to look at many characteristics and figure out which are useful, which are linked, which are just random variants, and so on. But a key point is that you don't necessarily need many instances of your new bone, just enough data from your comparison -- in this case, H. sapiens -- to know what's normal and what's way out of normal. Here (from http://en.wikipedia.org/wiki/Neanderthal_anatomy on Wikipedia) is a list of distinguishing characteristics for Neandertals.  You'd really want to look at as many as you can, to get as much support. Cranial Suprainiac fossa, a groove above the http://en.wikipedia.org/wiki/Inion http://en.wikipedia.org/wiki/Occipital_bun, a protuberance of the http://en.wikipedia.org/wiki/Occipital_bone, which looks like a hair knothttp://en.wikipedia.org/wiki/Neanderthal_anatomy#cite_note-Gunz-8 Projecting mid-face less http://en.wikipedia.org/wiki/Neoteny skull than humanshttp://en.wikipedia.org/wiki/Neanderthal_anatomy#cite_note-Montagu-6 Low, flat, elongated skull A flat basicraniumhttp://en.wikipedia.org/wiki/Neanderthal_anatomy#cite_note-9http://en.wikipedia.org/wiki/Neanderthal_anatomy#cite_note-10http://en.wikipedia.org/wiki/Neanderthal_anatomy#cite_note-11 http://en.wikipedia.org/wiki/Supraorbital_torus, a prominent, trabecular (spongy) brow ridge 1,500–1,900 cm3 (92–116 cu in) skull capacity (modern man: 1425 cm3) Lack of a protruding chin (mental protuberance; although later specimens possess a slight protuberance) Crest on the http://en.wikipedia.org/wiki/Mastoid_process behind the ear opening No groove on http://en.wikipedia.org/wiki/Canine_teeth A http://en.wikipedia.org/wiki/Retromolar_space posterior to the third molar Bony projections on the sides of the http://en.wikipedia.org/wiki/Nasal_bone opening, projecting http://en.wikipedia.org/wiki/Human_nose Distinctive shape of the bony http://en.wikipedia.org/wiki/Labyrinth_(inner_ear) in the ear Larger http://en.wikipedia.org/wiki/Mental_foramen in mandible for facial blood supply Sub-cranial Considerably more robust, stronger build Long http://en.wikipedia.org/wiki/Collar_bone, wider http://en.wikipedia.org/wiki/Shoulder Barrel-shaped http://en.wikipedia.org/wiki/Human_rib_cage Short, bowed http://en.wikipedia.org/wiki/Scapula More laterally curve http://en.wikipedia.org/wiki/Radius_(bone) with a http://en.wikipedia.org/wiki/Radial_tuberosity placed more medially, a longer radial neck, a more ovoid radial head, and a well-developed interosseous crest.http://en.wikipedia.org/wiki/Neanderthal_anatomy#cite_note-DeGroote-2011-12 On the http://en.wikipedia.org/wiki/Ulna, the http://en.wikipedia.org/wiki/Trochlear_notch is facing more anteriorly, the http://en.wikipedia.org/wiki/Brachialis_muscle insertion is lower, the mid-shaft is larger, and the shaft is more sinusoidal.http://en.wikipedia.org/wiki/Neanderthal_anatomy#cite_note-DeGroote-2011-12 Larger round http://en.wikipedia.org/wiki/Finger tips Large http://en.wikipedia.org/wiki/Kneecap Thick, bowed shaft of the http://en.wikipedia.org/wiki/Thigh_bone, bowed http://en.wikipedia.org/wiki/Femur Short http://en.wikipedia.org/wiki/Tibia and http://en.wikipedia.org/wiki/Fibula, longer http://en.wikipedia.org/wiki/Torso and proportionally shorter http://en.wikipedia.org/wiki/Human_leg Long, gracile pelvic http://en.wikipedia.org/wiki/Pubis_(bone) (http://en.wikipedia.org/wiki/Superior_pubic_ramus)