Sigh, common descent with modification can be tested. Just compare the DNA sequences between species. Of course, our genetic material is closest to primates, than let’s say a frog. Also, the fossils tell the story of evolution, (but unfortuantely we will never know the entire story).
Not everything is controlled by the DNA
Michael Denton agrees with when he states that the gene-centric theory of neo-Darwinism - is insufficient to explain all aspects of biology. He states “Yet by the late 1980s it was becoming obvious to most genetic researchers, including myself, since my own main research interest in the '80s and '90s was human genetics, that the heroic effort to find the information specifying life’s order in the genes had failed. There was no longer the slightest justification for believing that there exists anything in the genome remotely resembling a program capable of specifying in detail all the complex order of the phenotype… From being ‘isolated directors’ of a one-way game of life, genes are now considered to be interactive players in a dynamic two-way dance of almost unfathomable complexity, as described by Keller in “The Century of the Gene”
Michael John Denton ”An Anti-Darwin Intellectual Journey”, in Dembski, W. A. (ed) “Uncommon Dissent: Intellectuals who Find Darwinism Unconvincing”, p172.
He gives examples of the folds in RNA which happen consistently, and independently of genetic coding… but these rules governing the folds… “These laws of protein form are strictly equivalent to the rules that govern the way atoms are combined into molecules or subatomic particles are combined into atoms to generate the periodic table of elements…
The folds present stunning evidence, perhaps the first clear evidence discovered in biology, that highly complex organic forms can be generated by natural law. With the folds, the impossible has become possible - the basic building blocks of nature are specified in abstract laws of form and are not simply a mechanical program in the genes. They are lawful, emergent, self-organising forms and not contingent ‘cleverly contrived machines’. Here is a set of forms that arise directly out of the basic properties of matter, confirming the inference I had previously drawn from reading Henderson, that life might be encoded in the basic properties of matter.”
Ibid, pp173-74
You can use other measures to find we’re more closely related to other things
“There are, for instance, more than 800 species of frogs, all of which look superficially the same. But there is a greater variation of molecular structure between them than there is between the bat and the blue whale”
Milton, R., (1997) “Shattering the Myths of Darwinism”, (Park Street Press; Rochester, VT), p184
He also notes studies of protein sequences don’t help the evolutionary cause (Ibid., pp182-3)