Obvious phenotypic inheritance markers in humans In humans, are there phenotypic markers that prove parenthood? For example, if mother and father have `<trait characteristic>` (let's say, specific ear lobe form), then any child will have `<trait characteristic>`. If the child does not exhibit that characteristic, than either father or mother or both are only alleged, not actual.

No. To determine the genetic relationship (if any) between two individuals requires molecular evidence based on genetic markers in their somatic DNA. Using phenotypes _could_ be misleading because a genetic marker (an allele) can have variable penetrance (the percentage of carriers who actually have the phenotype) _and_ variable expressivity (the severity or degree of the phenotype). Some of this variability can come from gene-environment interactions, and some could come from epigenetic effects (ie non-heritable).