* DNA Degradation: Fossil remains are extremely old. DNA degrades rapidly over time, especially in the absence of ideal preservation conditions. Even with advanced techniques, retrieving intact DNA from such ancient specimens is extremely challenging.

* Contamination: Extracting and amplifying ancient DNA poses a significant risk of contamination with modern DNA. This can lead to false results.

* Fragmentation: The DNA that might remain in fossils is likely to be highly fragmented. PCR amplification requires relatively long stretches of intact DNA to work effectively.

Instead of PCR, researchers rely on other techniques for ancient DNA analysis, such as:

* Next-Generation Sequencing (NGS): NGS allows for the sequencing of fragmented DNA, which is more common in ancient samples.

* Ancient DNA Extraction Techniques: Specialized techniques are employed to carefully extract and purify DNA from ancient remains while minimizing contamination.

* Paleogenomics: This field focuses on studying ancient genomes, often utilizing NGS and advanced bioinformatics tools.

While amplifying DNA from fossils is a complex and challenging endeavor, it's a rapidly advancing field with ongoing research. We might see breakthroughs in the future that allow for more effective DNA analysis from such ancient samples.