in the brains of hominins. Recently, a new approach called 4E cognition (see Models for other approaches) has been developed by anthropologist Thomas Wynn, and cognitive archaeologists Karenleigh Overmann and Lambros Malafouris, to move past the "internal" and "external" dichotomy by treating stone tools as objects with agency in both providing insight to hominin cognition and having a role in the development of early hominin cognition. The 4E cognition approach describes cognition as embodied, embedded, enactive, and extended, to understand the interconnected nature between the mind, body, and environment. There are four major categories of tools created and used throughout human evolution that are associated with the corresponding evolution of the brain and intelligence. Stone tools such as flakes and cores used by Homo habilis for cracking bones to extract marrow, known as the Oldowan culture, make up the oldest major category of tools from about 2.5 and 1.6 million years ago. The development of stone tool technology suggests that our ancestors had the ability to hit cores with precision, taking into account the force and angle of the strike, and the cognitive planning and capacity to envision a desired outcome. Acheulean culture, associated with Homo erectus, is composed of bifacial, or double-sided, hand-axes, that "requires more planning and skill on the part of the toolmaker; he or she would need to be aware of principles of symmetry". In addition, some sites show evidence that selection of raw materials involved travel, advanced planning, cooperation, and thus communication with other hominins. The third major category of tool industry marked by its innovation in tool-making technique and use is the Mousterian culture. Compared to previous tool cultures, which were regularly discarded after use, Mousterian tools, associated with Neanderthals, were specialized, built to last, and "formed a true toolkit". The making of these tools, called the Levallois technique, involves a multi-step process which yields several tools. In combination with other data, the formation of this tool culture for hunting large mammals in groups evidences the development of speech for communication and complex planning capabilities. While previous tool cultures did not show great variation, the tools of early modern Homo sapiens are robust in the amount of artifacts and diversity in utility. There are several styles associated with this category of the Upper Paleolithic, such as blades, boomerangs, atlatls (spear throwers), and archery made from varying materials of stone, bone, teeth, and shell. Beyond