Numbers used to calculate data points in Figs 1–3, including those in Tables 1 and 2, are provided as a download-able dataset.

A few notes about the elements of this dataset are provided here: The list of 20 artificial systems analyzed is Kismet (2000), ASIMO (2000), PackBot (2001), Roomba (2002), RoboSapien (2003), BigDog (2005), KR 60 HA (2005), Aibo (2006), Keepon (2007), LittleDog (2007), NAO (2008), Simon (2009), Darwin (2010), PR2 (2010), RoboNaut2 (2010), Baxter (2012), Cheetah (2012), LBR iiwa (2013), HansonZeno (2013), and Khepera IV (2015). For the external element counts of artificial systems, many of these were determined through observation. The choice of 0.1 resolution, where not directly available, is supported by the use of this precision of encoders in the NAO platform [57], in a patent filed by FANUC Corp. for their industrial robots [61], and in a more recent patents on encoders by Bei Sensors and Systems Company, Inc. [62]. In these systems, encoders use optical sensors to detect light transmission through transparent regions on a circular disc; this analog signal is transmitted to digital representation, where the number of bits allotted can also impact resolution. A common number of transparencies is, as in the FANUC patent, 2500, and a common digital representation is 12 bits as in a more recent patent by Bei, allowing 4096 distinct positions. Across 360° both result in roughly 0.1° precision. In applications like laser jet printers, these devices can also achieve micrometer precision (roughly 1 million positions out of one rotation) as discussed in a patent from Lexmark International, Inc. [85]. To this author’s knowledge, such specialized, high-precision hardware is not common in the robots reviewed here. For the natural systems analyzed, the values used are based on [29, 63, 70–72, 74]. The list of 20 artificial systems analyzed is Kismet (2000), ASIMO (2000), PackBot (2001), Roomba (2002), RoboSapien (2003), BigDog (2005), KR 60 HA (2005), Aibo (2006), Keepon (2007), LittleDog (2007), NAO (2008), Simon (2009), Darwin (2010), PR2 (2010), RoboNaut2 (2010), Baxter (2012), Cheetah (2012), LBR iiwa (2013), HansonZeno (2013), and Khepera IV (2015). For the external element counts of artificial systems, many of these were determined through observation. The choice of 0.1 resolution, where not directly available, is supported by the use of this precision of encoders in the NAO platform [57], in a patent filed by FANUC Corp. for their industrial robots [61], and in a more recent patents on encoders by Bei Sensors and Systems Company, Inc. [62]. In these systems, encoders use optical sensors to detect light transmission through transparent regions on a circular disc; this analog signal is transmitted to digital representation, where the number of bits allotted can also impact resolution. A common number of transparencies is, as in the FANUC patent, 2500, and a common digital representation is 12 bits as in a more recent patent by Bei, allowing 4096 distinct positions. Across 360° both result in roughly 0.1° precision. In applications like laser jet printers, these devices can also achieve micrometer precision (roughly 1 million positions out of one rotation) as discussed in a patent from Lexmark International, Inc. [85]. To this author’s knowledge, such specialized, high-precision hardware is not common in the robots reviewed here. For the natural systems analyzed, the values used are based on [29, 63, 70–72, 74]. (XLSX)