both depend on flint for their tools; both recognize the importance of fire and use it; both hunt and gather. Physiologically, the Clan are heavier and broader but also shorter than the people of The Others. They are very slow to embrace change and to innovate, and they still chase after animals to spear them directly, whereas the Cro-Magnons are enthusiastic about innovation and have moved on to projectile spears. The Clan's tools, clothing, and household implements are similarly less refined and sometimes less effective than those of their Cro-Magnon counterparts, whose implements and other goods are more technologically sophisticated. The Clan's reluctance to change is depicted by Auel as a function of their cognition; they are presented as dependent upon their racial-genetic memory. The average Clan child needs only be 'reminded' of a thing to know it permanently, though skilled tasks still require repetitive practice. Furthermore, the need to encode everything into a child's brain has increased the average Neanderthal head size to the point that, by the time of the first novel, women of the Clan are having trouble giving birth to their large-headed babies—a sign that their evolutionary strategy has run its course. The "Flatheads", as "The Others" pejoratively call the Neanderthals (owing to their distinctive back-sloping foreheads), also have a far more limited vocal repertoire than The Others, and largely communicate instead via a gestural sign language, although spoken words are sometimes used to add emphasis to the gestures. Auel describes this language as being quite nuanced, especially as bodily posture, facial expression and other physical actions — in short, body language — can expedite and expand upon the basic vocabulary of the hand signals. A Cro-Magnon observing Ayla demonstrating a translation characterizes the language as dancelike and elegant. For this reason, Clan members are highly adept at reading body language and cannot be deceived by lying; while one can spell an untruth with one's hands, one's posture will give it away. Consequently, the idea of telling an untruth is alien to Clan culture, a fact that Ayla needs time to conceptualize and understand. However, a Clan member can "refrain from mentioning" something she would prefer other people did not know, even though residual clues would probably reveal that something was being concealed. Cultural conventions, Auel suggests, would cause other Clan members to ignore the concealment out of sheer courtesy, though, again, Ayla has trouble grasping