Niemitz (2002)
Classification: Habitat Compulsion
Mnemonic: Wading
Specific Model: Amphibische Generalistheorie
Original Proponent(s): Niemitz (2002)    
Basic Summary: Humans evolved from locomotor generalists that included a significant wading component in their locomotor repertoire.    
Assessment: Popularity: This model was classified under the subcategory, "wading habitat compulsion", and was ranked 7th most popular out of 9 categories  in the texts reviewed here. No text referred to this idea explicitly.
Simple: #5 /42 (74%)
Detailed: #4 / 42 (79%)
Discussion: A Theory on the Evolution of the Habitual Orthograde Human Bipedalism - The "Amphibische Generalistheorie" Niemitz (2002).
Carsten Niemitz (2002), a German anthropologist, published a comprehensive paper which promoted wading in shallow water as a key driver of hominid bipedalism.

Unlike Westernhöfer (1942), Hardy (1960), Morgan (1972, 1990, 1994, 1997) and Verhaegen et al (2000) before him, he suggested that gallery forest habitats would have played a prominent role in the process.

“The theory presented here suggests that our hominoid ancestor lived in gallery forests and changed strata in order also to inhabit the savannah habitat as well as the shallow water of rivers or coasts. Foraging in a wading manner was extremely favourable for an effective and, especially, seasonally independent, animal protein supply”
Niemitz (2002:3).

After a review of 14 major model types of bipedal origins, Niemitz begins to outline and evaluate his theory that of “an amphibious locomotor generalist as an ancestor of Homo - The ‘Amphibische Generalistentheorie’” (Niemitz 2002:11). The argument begins along the lines of Rose (1991) suggesting that humans, rather uniquely amongst primates, have a single mode of locomotion in their repertoire but Niemitz makes the point that although this is undoubtedly true, humans also are unique in their ability “without special training” to undertake a diverse array of locomotor tasks: walking 30km in one day, sprint 150m, jog over 1500m, climb up a tall tree, jump, after a run up, over a 3m wide ditch, dive to a depth of 2m to retrieve an object from the bottom and swim ‘fast’ for 200m. Niemitz claims that this combination of tasks could not be done by any other mammal, let alone any non-human primate. As he puts it “In spite of the apparent specialization for bipedal posture and locomotion, humans are amazing postural and locomotor generalists” (Niemitz 2002:11). Niemitz argues that this generalist capability suggests that the precursive form of locomotion could not have been highly specialised.

Niemitz suggest that the primate trend, because of their arboreality, is hind limb dominance. This, clearly, is an important precondition for the later evolution of human bipedality.

After some consideration of the evolution of the human hand and general body and limb proportions, Niemitz begins to consider the rather controversial idea that “we never came down from the trees” (Niemitz 2002:22). It is a curious view, considering his emphasis on gallery forest habitats in hominid evolution but it supported with good comparative evidence from various primate groups showing that generally larger species are less arboreal.

In a key statement, Niemitz supports Martin’s (1990) statement about primate evolution:
“For the reasons given here, I agree only partially with the following quote: "The ancestral similans were presumably still essentially arboreal in habitats", but I fully agree, when Martin continues: "... But there is increasing evidence that Old World Monkeys at least underwent a shift to more terrestrial habits that has left its mark on all modern representatives of this group (see : Andrews and Aiello 1984)"”
Niemitz (2002:26)

Niemitz then states his somewhat controversial assumption that the immediate precursor to human bipedalism “… never came down from the trees. They merely stayed where they were anyway – i.e. on the ground.” (Niemitz 2002:26), although its is conceded that they retained some ability to climb trees for food and for safety from predators. Unfortunately this argument does seem to be somewhat contradicted, if one assumes that gracile australopithecines, which were very diminutive in stature, approximated the general size and shape of the immediate precursors to the genus Homo. Indeed the idea that “we never came down from the trees” plays little part in a large of Niemitz’s argument: that adaptations to vertical climbing were important in the evolution of the orthograde orientation of the human body plan and retention of relatively long arms. And it seems to be absent from his thinking about australopithecines:
“The above aspects of functional anatomy and behavioural biology [orthogrady through vertical climbing] are also in accordance with the hypothesis that the australopithecines evolved their bipedal upright gait living in or at the border of the forest (e.g. Lovejoy 1980). When flying over the East African savannah today, the many green arteries of gallery forests are an impressive sight; they add up to a considerable portion of the area and have a prosperous diversity of life. The forests where bipedal australopithecines evolved were by no means necessarily vast primary forests. There, a species might be better off having chosen one alternative, either the canopy or the ground. However, the river and the savannah nearby may be good reasons to leave the upper stratum sometimes.”
Niemitz (2002:34)

Niemitz closes that section by suggesting that as chimpanzees are relatively large and predominantly terrestrial, apes both in relatively open and closed habitats, but are capable of climbing it leaves open the question of “the causal foundation of completely remodelled pelvic bones, long legs, a non grasping, fully re-constructed foot with a longitudinal and frontal arch” (Niemitz 2002:35.)

The second half of his paper presents his offered solution to this question by examining what he terms ‘amphibious non-aquatic and aquatic foraging’. Niemitz begins with an impressive catalogue of reports of wading, swimming and/or food procurement from aquatic or semi-aquatic sources in at least 21 primate species.
“These episodes clearly reflect that there is a much closer relationship between quite a number of primate species and life near the shore or even in the water than has been realised. In one way or another, these > 35 primate species have close relationships with water (see also below). If we include man (for reasons, see below), we have to list about 40 species. As we have seen, this also refers to our closest relatives.”
Niemitz (2002:39)

The association of primates with water is one that is not often recognised and is much more often neglected and Niemitz is clearly keen to persuade the reader that the evidence is already there to make such associations. Next Niemitz turns his attention to geological and paleoanthropological findings and cites La Lumiere’s paper which reported that the Danakil depression of the north eastern rift valley was inundated by the Red Sea around 4mya. Unfortunately, most of the evidence provided which indicates an association between human ancestors and waterside niches was from the time of Homo erectus and later, (even including data about recent fish imports from some countries and about holiday makers’ preferences for seaside locations) clearly much too late to have influenced the evolution of human bipedalism. After this, Niemitz returns to perhaps his most interesting observations, those pertaini Some human-ape differences which have been used as explanatory vehicles by the so-called “aquatic ape hypothesis” are given primacy in the early part of that discussion. In Niemitz’s words, “they will suffice to show that several of the main pillars of the theoretical building do not carry the theoretical construction” (Niemitz 2002:47), which I take to mean that Niemitz thinks these four characteristics do not indicate an adaptation to a fully aquatic (i.e. involving significant swimming/diving) niche. On the contrary, he cites the four traits: descended larynx (due to longer necks, and longer necks are adaptive to wading), ventro-ventro copulation (a result of bipedalism), an insulating fat layer (mainly, Niemitz claims, in the lower part of the body) and bipedalism (wading) as being better explained by what he terms his “Amphibisce Generalistheorie” (or ‘general amphibious theory’), in other words by bipedal wading.

He writes
“Summing up, almost all characters that have been used to lend support to the aquatic ape theory can be shown to be insignificant.”
Niemitz (2002:48)

Niemitz appears to be making a distinction between what he has classified as ‘swimming and diving’ adaptations (those cited by ‘AAH’ proponents) and ‘wading’ adaptations (those promoted by the ‘amphibisce generalistheorie’). This is clearly a false dichotomy as the wading hypothesis of hominid bipedal origins is one of the most compelling arguments made by Hardy (1960), Morgan (1972, 1990, 1994, 1997) and Verhaegen et al (2000). Compounding this contradiction, citing Morgan, Niemitz writes: “"The idea that bipedalism may have arisen as a consequence of wading behaviour is a hypothesis, just like all the others [outlined in her book], about which Morgan (1997) argues: None of them is proven". In contradiction to this statement, it is the aim of this article to show that a transient wading past in our ancestry is most likely.” Niemitz (2002:48)

Having distanced himself from the so-called ‘AAH’, Niemitz proceeds to construct a theoretical framework for wading in the evolution of human bipedalism based on an analysis of human long-leggedness.

His argument starts by suggesting that long-legged bipeds are very rare and most often found in wading birds and suggests four main selective advantages that would also arise form long leggedness in a hominin that regularly waded.
• Increasing leg length is likely to reduce the drag on the body whilst moving through most depths of water as it raises more of the torso above the surface.
• This also will lead to a reduction in buoyancy which would have the effect of increasing ground reaction forces, allowing the hominid to propel itself with greater force.
• In deeper water, having longer legs would increase the depth threshold at which a hominid would have to beginning swimming. This is likely to have selective advantage in reducing the risk of drowning.
• Having longer legs are more advantageous for wading than for swimming. This would have acted as a kind of negative feedback loop on increasing the degree of aquatic adaptation.

From there he suggests that the limb segment lengths of humans appear to be a compromise for wading, climbing and terrestrial locomotion: “This combination of characters (1. long hind limbs, 2. middle sized plantigrade foot and 3. hind limb muscles with not very long distal tendons) makes an excellent, optimised wader. At the same time, this human anatomy is a compromise that makes a perfect walker and a good long distance runner, but a less good sprinter.” Niemitz (2002:54) The argument is continued by suggesting that energetic disadvantages that are likely to be incurred by early hominid bipeds are compensated for by buoyancy in wading situations.

Niemitz concedes that such adaptive benefits in favour of upright posture and bipedal gait as may be expected in wading situations were unlikely to have resulted from only infrequent, short bursts of wading behaviour. He therefore proposes that “a truly amphibious stage seems quite probable” (Niemitz 2002:55), a view that turns out to be very close to that originally proposed by Hardy (1960). He summarises his argument by suggesting that “w[W]ading proved to be energetically a very rewarding way of foraging, especially for high quality animal protein. This was probably of decisive importance for the survival of some of our ancestors in - possibly seasonal - periods of scantiness of food outside the water. An ecological and locomotor generalist (opportunist) type of wading non-human primate is. at a certain stage of our evolution, a very probable ancestor to Homo, while the likelihood of being a descendant of a specialised type of primate is genetically very improbable.” Niemitz (2002:57)

The paper ends…
“While other mammals have enlarged and optimised their front limbs upon entering the water, the main reason for our bipedality on the hind limbs is, ultimately, the position of the centre of mass in the bodies of primates, while the second is our increased demand for animal protein. Third, there is a development changing the landscape with increasing savannah areas. Fourth, our ancestors could make use of this scenario best, or only by changing strata and habitats, using, fifth, the gallery forest in a climbing fashion, the water in a bipedally wading manner and, finally, the savannah as the only habitual orthograde bipedal walker.”
Niemitz (2002:57).
Strengths: Like all wading models Niemitz theory has a number of strengths such as providing a simple mechansim for survival and that it has good evidence in extant primates. Unlike most ideas it is also very strong in proving good biomechanical arguments for early bipedalism.
Weaknesses: The model was judged weakest in explaining early hominin postcranial anomalies largely because of a perceived contradiction between the australopithecine evidence and the model being proposed.    
1.1 Survival Value 9 (Good) All wading models provide a very simple and strong argument for survival - keeping the head above the water.    
1.2 Sexual Selection 5 (Fair) This model was judged neutral by this criterion.    
1.3 Not Teleological 9 (Good) This model is judged good by this criterion as it is based on a plausible rend of evolution toward greater generalisation.    
2.1 Improved Food Acquisition 6 (Fair) This model was judged better than neutral by this criterion as it places hominins in waterside habitats that are relatively rich in foods.    
2.2 Accounts for Predation 5 (Fair) Niemitz does not sidestep the issue of crocodile predation but points out that many primates have still been observed moving in water despite local infestation with crocodiles and that whatever threat of predation posed by them must be compared with the threat of predation on open habitats.    
2.3 Why Apes are not Bipedal 6 (Fair) Niemitz model was judged only slightly better than neutral on this criterion as it does not emphasise a specific habitat that would account for Pan-Homo-Gorilla divergence.    
2.4 Extant Analogues 8 (Good) This model provides good evidence of analogous behaviour in extant apes and other primates.    
2.5 Applies to Both Sexes 9 (Good) Niemitz's model applies equally to both sexes.    
3.1 Hominid Anomalies 3 (Poor) This appears to be a weakness in Niemitz’s specific model as he, perhaps oddly, makes the claim that human ancestors “never came down from the trees.” He does so largely on the evidence that in each primate group the largest ones tend to be more terrestrial. However, assuming the immediate precursor to the Homo genus was either a gracile australopithecine or at least australopithecine like, this argument is strongly contradicted by their diminutive size and their clear anatomical traits indicating arboreality. Perhaps Niemitz is suggesting that the ancestors of Homo lay elsewhere, but it is certainly a weakness that his model does not really attempt to address the differences in post cranial morphology between australopithecines and humans.    
3.2 Fits Paleoecological Record 9 (Good) His model’s assumption of gallery forest habitats for early human ancestors appears to be very consistent with the growing paleoecological record for such species    
3.3 Precursor to Strider and knuckle Walker 9 (Good) Niemitz makes a very strong case that the biomechanics of efficient wading in a variety of depths very much overlaps with the anatomical requirements for human bipedalism    
4.1 Extended Explanatory Power 5 (Fair) Niemitz limits himself to explaining bipedal origins although his does imply that the human attarction to waterside locations may also be accounted for by this.    
4.2 Complimentary 6 (Fair) Niemitz's model was judged complimentary to most other models and compatible with all others apart from Rodman & McHenry's energy efficiency model and Leiberman's Endurance Running model.    
4.3 Falsifiable or Testable 5 (Fair) This model was judged neutral on this criterion.  
References Niemitz, C. (2002) A Theory on the Evolution of the Habitual Orthograde Human Bipedalism - The "Amphibische Generalistheorie". Anthropologischer Anzeiger 60:3-66.
Niemitz, C. (2010) The evolution of the upright posture and gait—a review and a new synthesis. Naturwissenschaften.