Final answer:
Fossils of archaic Homo sapiens and Homo erectus show a reduction in skeletal robusticity and tooth size, along with brain expansion and increased cultural complexity, with evidence in the fossil record supporting both these trends.
Step-by-step explanation:
All fossils of archaic Homo sapiens and earlier Homo erectus show both continued reduction in skeletal robusticity and tooth size, and an expansion of the brain and increased cultural complexity. This includes a progressive increase in brain size seen in H. erectus which presents a clear trend from about 550 cc to 1,250 cc, alongside evidence of the use of fire and more complex tool-making, which are indicative of increased cognitive capabilities and cultural development. Concurrently, the adoption of softer, cooked foods led to smaller teeth, while other skeletal changes facilitated increased brain capacity and bipedal efficiency. Brain size growth, or encephalization, in human evolution began with Homo habilis and progressed more markedly through H. erectus, which is correlated with enhanced cognitive, behavioral, and cultural complexity. Archaic Homo species display this trend, with brain sizes ranging around 1,200 to 1,400 cc, similar to modern humans but with unique morphological features such as a thick skull and prominent brow ridges.
Regarding the traits of these hominin species, options a. and b. would be correct since they reflect the evolutionary trends towards reduced robusticity of the skeleton and teeth, as well as brain expansion and cultural complexity, as seen in the fossil record of Homo erectus and archaic Homo sapiens.