Monkey's uncle

i) One of the prima facie challenges for Bible-believing Christians is how, if at all, we are related to extinct "hominids." I'm going to use "hominid" for convenience. By conventional definition, that term implies a relationship. My use of the term doesn't prejudge our relationship, if any. I use it for ease of reference.

I'm no expert, but since Christians are expected to take a position on this issue, I'll give my 2¢, 

ii) In terms of fossil evidence, from what I've read this usually consists of skeletal fragments, sometimes collected from different sites. So our understanding (if you can call it that) of extinct hominids usually consists of composite reconstructions, in which paleoanthropologists rearrange fragments into an assumed pattern, resorting many interpolations and extrapolations to fill in the trace evidence.

More recently, this has been supplemented by comparative genomics. 

Our popular impression of extinct hominids is based on highly imaginative artistic representations. The raw evidence in situ is far more ambiguous. Or so I've read, from multiple sources.

iii) Both Darwinians and creationists often make very self-confident statements regarding the human or inhuman status of fossil hominid evidence. From what I can tell, their confidence is often overrated. Due to the shifting sands of paleoanthropology, remains are frequently reclassified. 

iv) On YEC chronology, extinct hominid remains are postdiluvial. On OEC chronology, extinct hominid remains could be prediluvial to varying degrees. 

v) One putative evidence for human evolution is encephalization. Bigger brains indicate a later stage in human development–or so goes the argument. But that's subject to significant qualifications:

a) To some extent, brain size is correlated to body size. How much did a given hominid weigh? A smaller brain of a smaller hominid might be proportional to a human brain. So we must make allowance for the brain to body mass ratio.

b) The relationship between brainpower and intelligence is mysterious. Social insects famously exhibit intelligent behavior. Even the lowly amoeba exhibits intelligent behavior. That's not attributable to brainpower. How to interpret intelligent behavior in "brainless" organisms poses an interesting question. At the very least, they mimic intelligence. And that's something to take into account when we try to gauge the intelligence of extinct hominids from trace evidence of intelligent behavior. That can be deeply misleading. We are tacitly using ourselves as the frame of reference, because we understand what that would mean if we were doing it. Yet we discount that facile inference in the case of "brainless" organisms.

vi) The definition of "species" in modern biology is unsettled There are competing concepts. Wider and narrower definitions. 

vii) Did some hominids actually become extinct? Or were some of them absorbed into "modern man" through interbreeding? 

viii) Consider all the different dog breeds. If all dogs became extinct, and all we had to go by were skeletal fragments, imagine a Darwinian arranging the fossil evidence into an evolutionary sequence of different species. Proto-dogs. Imagine how Darwinians would fight over the right classification for this or that canine fossil. 

ix) To some extent, human eidonomy is adaptive to climatic conditions. If all paleoanthropologists had to go by were skeletal remains of Eskimos, Maasai, and Watutsi, would they classify these as members of the same species or different species? Would they arrange them in an evolutionary sequence?

x) Suppose the great apes (bonobos, chimpanzees, gorillas, and orangutans) were extinct. Would paleoanthropologists classify them as hominids? 

xi) Apropos (x), compare the great apes to Australopithecus or Homo erectus. Because chimps, gorillas, and orangutans are our contemporaries, because we can study them, both in the wild and in the laboratory, we have a fairly good understanding of how they are both like and unlike us. As one wag put it:

The idea that human beings have been endowed with powers and properties not found elsewhere in the animal kingdom–or the universe, so far as we can tell–arises from a simple imperative: Just look around. It is an imperative that survives the invitation fraternally to consider the great apes. The apes are, after all, behind the bars of their cages and we are not. Eager for the experiments to begin, they are impatient for their food to be served. They seem impatient for little else. After years of punishing trials, a few of them have been taught the rudiments of various primitive symbol systems. Having been given the gift of language, they have nothing to say. When two simian prodigies meet, they fling their signs at one another. More is expected, but more is rarely forthcoming. Experiments conducted by Dorothy Cheney and Robert Seyfarth–and they are exquisite–indicate that like other mammals, baboons have a rich inner world, something that only the intellectual shambles of behavioral psychology could ever have placed in doubt. Simian social structures are often intricate. Chimpanzees, bonobos, and gorillas reason; they form plans; they have preferences; they are cunning; they have passions and desires; and they suffer. The same is true of cats, I might add. In much of this, we see ourselves. But beyond what we have in common with the apes, we have nothing in common, and while the similarities are interesting, the differences are profound. D. Berlinski, The Devil's Delusion (Crown Forum 2008), 155-56. 

Keep that in mind when paleoanthropologists draw confident inferences about the humanity of extinct hominids. Appearances are often deceptive. If the great apes were extinct, imagine how paleoanthropologists might readily overinterpret the signs of their incipient humanity. But because they happen to be our contemporaries, we have a direct basis of comparison. By contrast, that's conspicuously lacking in the case of extinct hominids. 

In the case of "cave men" who left paintings and petroglyphs, we can see human intelligence staring back at us. But that's exceptional evidence.